WO2012127212A1

WO2012127212A1 - Imidazo [1, 2 - b] pyridazine derivatives as cdpk1 inhibitors

Info

Publication number: WO2012127212A1
Application number: PCT/GB2012/050581
Authority: WO
Inventors: Simon Osborne; Timothy Chapman; Claire Wallace
Original assignee: Medical Research Council Technology
Priority date: 2011-03-18
Filing date: 2012-03-16
Publication date: 2012-09-27
Also published as: GB201104669D0

Abstract

A first aspect of the invention relates to a compound of formula (I), or a pharmaceutically acceptable salt or ester thereof, (Formula (I)) wherein: R¹ is -(CH₂)_nNR³R⁴, -OR⁵ or -(CH₂)_n-heterocycloalkyl, wherein said heterocycloalkyl group is optionally substituted by one or more R⁷ groups; R² is selected from aryl, heteroaryl, fused aryl-heterocycloalkyl and fused hetero aryl-heterocycloalkyl each of which is substituted by at least one R⁸ group; R³ is H or alkyl; R⁴ is: (i) cycloalkyl optionally substituted by one or more -NR¹¹R¹² or NHCOR¹¹ groups; or (ii) -(CH₂)_n-heterocycloalkyl, wherein said heterocycloalkyl is a 4, 5 or 6-membered nitrogen-containing group optionally containing one or more CO groups, wherein said heterocycloalkyl is optionally substituted by one or more one or more (CH₂)_nR⁷ groups; or (iii) alkyl substituted by one or more -NR¹¹R¹²groups; or R³ and R⁴ are linked together with the nitrogen to which they are attached to form a 4, 5, 6 or 7-membered monocyclic heterocycloalkyl group or a bicyclic heterocyclic group, each of which optionally contains one or two further groups selected from CO, O, N and S, and which is optionally further substituted by one or more R⁷ groups; R⁵ is selected from alkyl, -(CH₂)_n-heteroaryl and - (CH₂)_n-heterocycloalkyl, wherein said heteroaryl and heterocycloalkyl groups are each optionally substituted by one or more R⁷ groups; each R⁸ is independently selected from - NR¹⁶R17, -OR¹⁷ and -(CH₂)_nR¹⁷ where each R¹⁶ is H and each R¹⁷ is independently - (CHR¹⁰)_n-heteroaryl, wherein said heteroaryl group is in turn optionally substituted by one or more R⁷ groups; each R¹⁰, R¹¹ and R¹² is independently H or alkyl; or in the case of an - NR¹¹R¹² group, R¹¹ and R¹² may be linked together with the nitrogen to which they are attached to form a 4, 5, 6 or 7-membered monocyclic or bicyclic heterocycloalkyl group optionally containing one or two further groups selected from CO, O, N and S, and which is optionally further substituted by one or more R⁷ groups; each m is independently an integer from 1 to 6; and each n is independently an integer from 0 to 6. Further aspects relate to the use of said compounds in the treatment of various therapeutic disorders, and more particularly as inhibitors of PfCDPK1.

Description

COMPOUND

The present invention relates to fused heteroaromatic compounds that are capable of inhibiting CDPK1. The compounds have therapeutic applications in the treatment of malaria.

BACKGROUND TO THE INVENTION

Malaria remains one of the most important infectious diseases of the developing world. Up to 3 billion people are at risk, and each year there are 300-660 million clinical cases and at least 1 million children in Africa alone die of malaria, the biggest single killer of children under 5 in Africa. The failure of cheap and once effective drugs such as chloroquine due to parasite resistance has at last intensified the search for novel antimalarial compounds. Although Artemisinin combination therapy offers some respite in the short term, there is a desperate need for new drugs against new molecular targets. Although Plasmodium falciparum accounts for 75% of malaria cases and most of the deaths, P. vivax is also a significant problem worldwide.

The two most widely used anti-malarial drugs are chloroquine (CQ), a 4-aminoquinoline first synthesised in the 1930s as a substitute for quinine, and sulphadoxine-pyrimethamine (SP, commonly available as Fansidar). For several decades CQ was the gold standard for treatment; it was efficacious, has low toxicity and was affordable (less than US$0.2 for a 3 day adult course of treatment). CQ's mode of action is to interfere with haem detoxification in the parasite's food vacuole by preventing the formation of haemozoin. Following widespread use in the 1940s, CQ resistance started to emerge a decade later. CQ resistance has now spread to the vast majority of malaria endemic countries. However, it continues to be used. SP is a combination treatment and emerged from the success of proguanil, a pyrimidine derivative, as an antimalarial during World War 2. It targets folate metabolism (dihydrofolate reductase and dihydrofolate synthase) and is the other widely used inexpensive antimalarial drug, but as with CQ resistance is increasing. There is now an urgent need for new drugs with rapid efficacy, minimal toxicity and low cost to replace CQ and SP, which are failing due to widespread resistance in P. falciparum. Other drugs that have been used for malaria treatment include Mefloquine, a calmodulin antagonist, developed for prophylaxis, but also used successfully for treatment. Resistance appeared rapidly after the drug became generally available and unwanted side effects have been frequently reported. Malarone (a proguanil/atovaquone combination) is still largely effective but very expensive. Artemisinin, a natural product isolated from Artemisia annua, and derivatives such as artemether and artesunate are highly effective against malaria and as yet no cases of Artemisinin resistance have been reliably confirmed. Artemisinin is also the only agent to date that has been reported to block transmission of the parasite to mosquitoes. However, there are issues which need to be addressed, such as its short half life, purifying enough from natural sources or finding inexpensive synthetic routes. The use of Artemisinin and its derivatives, which have good efficacy but very short half-lives, together with longer acting agents such as amodiaquine or lumefantrine in Artemisinin-based combination therapy (ACT), offers some respite. However, these drugs are expensive and development of resistance is an ever present possibility.

New drugs are being developed and the most advanced are improved versions of existing treatments: Amodiaquine (CQ-like), chloroproguanil-dapsone (LapDap, an antifolate combination that inhibits the same enzymes as SP) and DB289 (an improved pentamidine; pentamidines have been used clinically against a range of infectious agents, but have toxicity issues).

It is becoming increasingly accepted that for control of malaria in developing countries drug combinations will be necessary, ideally attacking distinct parasite-specific biochemical pathways or processes. Combinations for uncomplicated malaria have the following potential advantages over monotherapy:

• Improved efficacy: Ideally a combination therapy should be at least additive in potency. While some may even be synergistic (e.g. SP), this may be a disadvantage since resistance to either component would impact on efficacy.

• In areas where drug resistance is common there is an increased likelihood that one of the agents will continue to be active, e.g. in East Africa there is resistance to both amodiaquine (CQ-like) and SP, but the combination still provides good anti-malaria cover. • Drug combinations can reduce the selection of resistance, as observed in Thailand with the use of an artesunate and mefloquine combination.

• With combinations it may also be possible to decrease doses of individual agents and thus reduce toxicity and cost.

Malaria parasites develop and multiply within red blood cells to form merozoites, which are the stage of Plasmodium that invades red blood cells to initiate a new cycle of development and replication. This asexual multiplication cycle of the parasite in the blood is responsible for causing all of the clinical symptoms of malaria. For transmission through the mosquito vector some parasites develop into gametocytes, the first stage of commitment to the sexual development that occurs primarily in the mosquito gut.

The asexual development and multiplication of the parasite in red blood cells is the obvious cellular target since this stage of the life cycle is responsible for manifestation of the disease. Parasite multiplication requires formation and release of merozoites that invade fresh red blood cells. Invasion is driven by a parasite actomyosin motor that has to be turned on at the right time; if merozoites cannot invade red cells they die, multiplication is prevented, and the infection is cleared. Activation of an actomyosin motor that drives the parasite into the host cell, is the same basic mechanism used by invasive stages of all apicomplexan parasites to enter host cells and for gliding motility. In the case of merozoite invasion of red blood cells a cascade of events results in parasite receptors engaging with ligands on the red cell surface and motor driven entry into the cell. If invasion is inhibited then the parasite dies and the asexual multiplication is interrupted. There is abundant evidence for the role of protein kinases in the control of invasion and a key member of this class of enzyme is a plant-type calcium dependent protein kinase (CDPK1) not found in mammals. Plasmodium falciparum CDPK1 is coded by an essential gene (that cannot be knocked out) and phosphorylates at least two components of the motor machinery. Inhibition of the corresponding Toxoplasma gondii CDPK1 with a kinase inhibitor impedes gliding motility and cell invasion, and other inhibitors of the motor effectively prevent merozoite invasion of red blood cells. Calcium-dependent protein kinases (CDPKs) are found only in plants and ciliates and are unique in that they are bipartite enzymes, containing a kinase domain and a regulatory domain. They are directly regulated by Ca²⁺, via its interaction with the calmodulin-like regulatory domain of the kinase. In the presence of calcium a conformation change is thought to result in activation of the kinase by release of the inhibitory junction domain from the active site.

P. falciparum CDPK1 is a Ser/Thr protein kinase member of this family, which is associated with the plasma membrane of merozoites via dual acylation of its N-terminus (J.L.G. unpublished data, Moskes et al., 2004). It is also expressed (at lower levels) in gametocytes. CDPK1 appears to be an essential enzyme, as attempts to knock out the gene in P. falciparum, or the orthologous gene in the rodent parasite P. berghei, have failed (Winzeler group, abstract, Molecular Parasitology meeting, Woods Hole, 2007; R. Tewari, personal communication). An inhibitor of CDPK1 would be expected to block the invasion of erythrocytes by merozoites and may also interfere with gametocytogenesis due to the presence of CDPK1 at lower levels in this first stage of the sexual cycle. A compound active against all CDPKs has the potential to be effective at several other stages of the life cycle including the invasive sporozoite stage. Whilst these other stages are asymptomatic clinically, they are important in terms of drug treatment. Sporozoites are responsible for the initial infection of the human host and gametocytes are the first stage in the cycle of transmission to the mosquito. Targeting these different stages of Plasmodium as well as the asexual stage responsible for the disease may be most effective for both prophylatic and treatment regimes. In the related parasite Toxoplasma gondii, treatment of parasites with the kinase inhibitor KT5926 blocked motility and cell attachment of invasive tachyzoites. Only one KT5926- sensitive activity that cofractionated with 7gCDPK1 was found in T. gondii and 7gCDPK1 is inhibited by KT5926 at the same concentrations that block motility of tachyzoites (Kieschnick et al. 2001). Other members of the CDPK family are expressed at different stages of Plasmodium. For example, CDPK3 is expressed in ookinetes - a stage of the parasite that is found in the mosquito vector. Ookinetes are motile and invade the mosquito midgut wall prior to forming oocysts. CDPK3-knockout P. berghei parasites show reduced motility and very few of the parasites are able to invade the mosquito midgut to form the oocysts where sporozoites develop. Interestingly, sporozoites from CDPK3-knockout parasites are motile and indistinguishable from wild type parasites suggesting stage- specific expression and activity of CDPKs (Ishino et al. 2006; Siden-Kiamos et al., 2006).

CDPK1 is the only member of the CDPK family that is expressed in significant amounts in merozoites. Given that inhibiting (7. gondii) or knocking out (P. berghei) CDPKs results in impaired motility, the ability of recombinant P/CDPK1 to phosphorylate components of the motor complex of P. falciparum was tested, namely myosin tail domain interacting protein (MTIP, a myosin light chain) and the 45 kDa gliding associated protein (GAP45). MTIP, GAP45, Myosin A (MyoA) and GAP50 are present in a heterotetrameric complex at the inner membrane complex (IMC) of the invasive stages of Plasmodium (Baum et al., 2006a, Green et al., 2006). GAP45 is a membrane-anchored protein of unknown function. Like CDPK1 , it undergoes dual acylation of its N-terminus resulting in the addition of myristate and palmitate groups that, together, are capable of providing a stable membrane anchorage (Rees-Channer et al., 2006). MTIP binds strongly to the short tail of MyoA, and shares homology with calmodulin and related proteins such as myosin light chains. The force required for the parasite to invade its host cell is generated by translocation of actin filaments by MyoA. The actin filaments themselves are linked, via an interaction with fructose-1 ,6-bisphosphate aldolase, to adhesins that traverse the parasite plasma membrane and interact with receptors on the host cell surface. The net result of the power stroke of Myosin A is forward propulsion of the parasite into a parasitophorous vacuole within the host cell. Using an assay that measures the incorporation of radiolabeled phosphate from [γ-^3ΖΡ] ATP into a substrate, it was found that recombinant CDPK1 was able to phosphorylate both MTIP and GAP45. The phosphorylation was absolutely calcium-dependent, and was abolished if a kinase-dead mutant of CDPK1 was used.

By way of summary,

• PfCDPKI is expressed at the relevant stage of the parasite's life cycle (that causes the disease) and has an intracellular location consistent with a role in merozoite invasion of red cells. • Attempts to knock out the CDPK1 gene have been unsuccessful indicating that it is essential for this stage of the parasite's development and multiplication.

β Recombinant P/CDPK1 can be inhibited by several compounds from the BIOMOL kinase inhibitor library, encouraging us to believe that CDPK1 can be targeted and inhibited by small molecules.

• PfCDPKI phosphorylates at least two components of the parasite motor complex; it is known that other inhibitors of the motor such as BDM (acting on MyoA), cytochalasin D (acting on actin) and myoA tail peptide (disrupting the MTIP-MyoA interaction) result in an inability of merozoites to enter red blood cells and therefore death.

• TgCDPKI is inhibited by KT5926 that stops parasite motility and cell invasion.

The present invention seeks to provide compounds which display a high degree of activity and/or specificity to CDPK and may therefore serve as drug candidates for treating malaria, or as a starting point for further derivatisation and kinase inhibition studies.

STATEMENT OF INVENTION

A first aspect of the invention relates to a compound of formula I, or a pharmaceutically acceptable salt or ester thereof,

(I)

wherein:

R¹ is -(CH₂)_nNR³R⁴, -OR⁵ or -(CH_z)_n-heterocycloalkyl, wherein said heterocycloalkyl group is optionally substituted by one or more R⁷ groups;

R² is selected from aryl, heteroaryl, fused aryl-heterocycloalkyl and fused hetero aryl-heterocycloalkyl each of which is substituted by at least one R⁸ group, and optionally further substituted by one or more R⁷ groups;

R³ is H or alkyl;

R is: (i) cycloalkyl optionally substituted by one or more -NR¹¹R¹² or NHCOR ¹ groups; or

(ii) -(CH₂)n-heterocycloalkyl, wherein said heterocycloalkyi is a 4, 5 or 6-membered nitrogen-containing group optionally containing one or more CO groups, wherein said heterocycloalkyi is optionally substituted by one or more one or more (CH₂)_nR⁷ groups; or

(iii) alkyl substituted by one or more -NR¹¹R¹²groups; or

R³ and R are linked together with the nitrogen to which they are attached to form a 4, 5, 6 or 7-membered monocyclic heterocycloalkyi group or a bicyclic heterocycloalkyi group, each of which optionally contains one or two further groups selected from CO, O, N and S, and which is optionally further substituted by one or more R⁷ groups;

R⁵ is selected from alkyl, -(CH₂)_n-heteroaryl and -(CH₂)_n-heterocycloalkyl, wherein said heteroaryl and heterocycloalkyi groups are each optionally substituted by one or more R⁷ groups;

each R⁷ is independently selected from -(CH₂)_nNR¹ R¹², halo, CN, nitro, -COR¹¹, - CONR¹¹R¹², alkyl, haloalkyl, haloalkyoxy, -OR¹¹, -NHC0₂R¹¹, -NHCOR¹¹, -NHS0₂R¹¹ and - C0₂R¹¹;

each R⁸ is independently selected from -NR¹⁶R¹⁷, -OR¹⁷ and -(CH₂)_nR¹⁷ where each R ⁶ is H and each R ⁷ is independently -(CHR¹⁰)_n-heteroaryl, wherein said heteroaryl group is in turn optionally substituted by one or more R⁷ groups;

each R¹⁰, R¹¹ and R¹² is independently H or alkyl; or in the case of an -NR¹¹R¹² group, R¹¹ and R¹² may be linked together with the nitrogen to which they are attached to form a 4, 5, 6 or 7-membered monocyclic or bicyclic heterocycloalkyi group optionally containing one or two further groups selected from CO, O, N and S, and which is optionally further substituted by one or more R⁷ groups;

each m is independently an integer from 1 to 6; and

each n is independently an integer from 0 to 6.

As is demonstrated in accompanying Examples section, representative compounds of the present invention were tested for their kinase inhibition activity and showed significant potency to CDPK1. These compounds can therefore efficiently serve for treating diseases or disorders in which inhibiting the activity of CDPK1 would be beneficial. A second aspect of the invention relates to a pharmaceutical composition comprising a compound as defined above admixed with a pharmaceutically acceptable diluent, excipient or carrier. A third aspect of the invention relates to a compound as described above for use in medicine.

A fourth aspect of the invention relates to a compound as described above for use in treating a CDPK1 -related disease or disorder, such as malaria.

A fifth aspect of the invention relates to a method of treating a CDPK1 -related disease or disorder.

A sixth aspect of the invention relates to a method of treating a mammal having a disease state alleviated by the inhibition of CDPK1 , wherein the method comprises administering to a mammal a therapeutically effective amount of a compound as described above.

A seventh aspect of the invention relates to the use of a compound as described above in an assay for identifying further candidate compounds capable of inhibiting CDPK1.

An eighth aspect of the invention relates to a process for preparing a compound as described above.

DETAILED DESCRIPTION

A first aspect of the invention relates to a compound of formula I as described above.

"Alkyl" is defined herein as a straight-chain or branched alkyl radical, for example, methyl, ethyl, propyl, isopropyl, butyl, isobutyl, ferf-butyl, pentyl, hexyl. Preferably, the alkyl group is a Ci_-20 alkyl group, more preferably, a C_1-12 alkyl group, even more prefereably, a C_1-B alkyl group, more preferably still, a C _-4 group. "Cycloalkyl" is defined herein as a monocyclic alkyl ring, such as, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl or cycloheptyl. Preferably, the cycloalkyl group is a C₃-i₂ cycloalkyl group, more preferably a C₃.₈ cycloalkyl group, more preferably still, a C_3-6 cycloalkyl group. As used herein, the term "aryl" refers to a monoaromatic or polyaromatic system, wherein said polyaromatic system may be fused or unfused. Preferably, the term "aryl" includes groups having from 6 to 12 carbon atoms, e.g. phenyl, naphthyl etc. The term "aryl" is synonymous with the term "aromatic". "Halogen" is defined herein as chloro, fluoro, bromo or iodo.

"Haloalkyl" is defined herein as an alkyl group, as defined above, which may be substituted in any position by one or more halogen radicals. "Alkoxy" is defined herein as an -O-alkyl group, wherein alkyl is as defined above.

"Haloalkoxy" is defined as an alkoxy group, as defined above, which is substituted in any position by one or more halogen radicals. "Heteroaryl" is defined herein as a monocyclic or bicyclic C3_₁₂ aromatic ring comprising one or more heteroatoms (that may be the same or different), such as oxygen, nitrogen or sulfur. Examples of suitable heteroaryl groups include thienyl, furanyl, pyrrolyl, pyridinyl, oxazolyl, thiazolyl, imidazolyl, pyrazolyl, isoxazolyl, isothiazolyl, oxadiazolyl, triazolyl, thiadiazolyl etc. and benzo derivatives thereof, such as benzofuranyl, benzothienyl, benzimidazolyl, indolyl, isoindolyl, indazolyl etc.; or pyridyl, pyrazinyl, pyrimidinyl, pyridazinyl, triazinyl etc. and benzo derivatives thereof, such as quinolinyl, isoquinolinyl, cinnolinyl, phthalazinyl, quinazolinyl, quinoxalinyl, naphthyridinyl etc.

"Heterocycloalkyl" refers to a cyclic aliphatic group containing one or more heteroatoms selected from nitrogen, oxygen and sulfur, which is optionally interrupted by one or more (CO) groups in the ring and/or which optionally contains one or more double bonds in the ring. Preferably, the heterocycloalkyl group comprises 3-6 carbon atoms and is fully saturated. Preferred heterocycloalkyi groups include piperidinyl, pyrrolidinyl, piperazinyl, thiomorpholinyl and morpholinyl. More preferably, the heterocycloalkyi group is selected from N-piperidinyl, N-pyrrolidinyl, N-piperazinyl, N-thiomorpholinyl and N-morpholinyl. In one preferred aspect of the invention relates to a compound of formula I, or a pharmaceutically acceptable salt or ester thereof

(I)

wherein:

R¹ is -(CH₂)_nNR³R⁴ or -OR⁵;

R³ is H or alkyl;

R⁴ is:

(i) cycloalkyl optionally substituted by one or more -NR R^1Z or NHCOR¹¹ groups; or

(ii) -(CH₂)_n-heterocycloalkyl, wherein said heterocycloalkyi is a 4, 5 or 6-membered nitrogen-containing group optionally containing one or more CO groups, wherein said heterocycloalkyi is optionally substituted by one or more one or more (CH₂)_nR⁷ groups; or

(iii) alkyl substituted by one or more -NR¹¹R¹²groups; or

R³ and R⁴ are linked together with the nitrogen to which they are attached to form a 4, 5, 6 or 7-membered heterocycloalkyi group which optionally contains one or two further groups selected from CO, O, N and S, and which is optionally further substituted by one or more R⁷ groups;

R⁵ is selected from alkyl, -(CH₂)_n-heteroaryl and -(CH₂)_n-heterocycloalkyl, wherein said heteroaryl and heterocycloalkyi groups are each optionally substituted by one or more R⁷ groups; each R⁷ is independently selected from -(CH₂)_nNR¹¹R¹², halo, CN, nitro, -COR¹¹, - CONR¹¹R¹², alkyl, haloalkyl, haloalkyoxy, -OR¹¹, -NHC0₂R¹¹, -NHCOR¹¹, -NHS0₂R¹¹ and - C0₂R¹¹;

each R⁸ is independently selected from -NR ⁶R ⁷, -OR¹⁷ and -(CH₂)_mR¹⁷ where each R¹⁶ is H and each R¹⁷ is independently -(CHR ⁰)_n-heteroaryl, wherein said heteroaryl group is in turn optionally substituted by one or more R⁷ groups;

each R¹⁰, R¹¹ and R¹² is independently H or alkyl; or in the case of an -NR ¹R^1Z group, R¹ and R¹² may be linked together with the nitrogen to which they are attached to form a 4, 5, 6 or 7-membered monocyclic or bicyclic heterocycloalkyi group optionally containing one or two further groups selected from CO, O, N and S, and which is optionally further substituted by one or more R⁷ groups;

each m is independently an integer from 1 to 6; and

each n is independently an integer from 0 to 6. In one preferred embodiment, R² is a heteroaryl group or a fused aryl-heterocycloalkyl group, each of which is substituted by at least one R⁸ group, and optionally further substituted by one or more R⁷ groups, and wherein said heterocycloalkyi group is a 5 or 6- membered nitrogen-containing group optionally containing one or more CO groups. In one preferred embodiment, R² is a heteroaryl group substituted by at least one R⁸ group, and optionally further substituted by one or more R⁷ groups.

In one preferred embodiment, R² is:

(i) a pyrimidinyl group substituted by one or more R⁸ groups;

(ii) a pyridinyl group substituted by one or more R⁸ groups;

(iii) a phenyl group substituted by by one or more R⁸ groups;

(iv) an indolyl group substituted by one or more R⁸ groups;

(v) an indazolyl group substituted by one or more R⁸ groups;

(vi) a benzimidazolyl group substituted by one or more R⁸ groups;

(vii) a pyrazolyl group substituted by one or more R⁸ groups;

(viii) a pyrazolopyridinyl group substituted by one or more R⁸ groups;

(ix) a fused aryl-heterocycloalkyl group which is

substituted by one or more R^B groups.

In one preferred embodiment, R² is a pyrimidinyl group substituted by at least one R⁸ group, and optionally further substituted by one or more R⁷ groups. More preferably, R² is a pyrimidin-5-yl group substituted by one or more R⁸ groups.

In one preferred embodiment, R^z is a pyrimidinyl group substituted by one or more groups selected from -NR¹⁶R¹⁷ and -OR¹⁷, wherein R ⁶ is H and R¹⁷ is (CH₂)_n-heteroaryl, wherein said heteroaryi is selected from pyrimidinyl, pyridinyl, pyrazolyl, pyrazinyl, pyridazinyl, quinolinyl, isoquinolinyl, quinazolinyl and quinoxalinyl, each of which is optionally further substituted by one or more R⁷ groups.

In one preferred embodiment, R² is a pyrimidinyl group substituted by one or more groups selected from -NR¹⁶R ⁷ and -OR¹⁷, wherein R¹⁶ is H and R¹⁷ is (CH₂)_n-heteroaryl, wherein said heteroaryi is selected from pyrimidinyl, pyridinyl, pyrazolyl, pyrazinyl, pyridazinyl, quinolinyl, isoquinolinyl, quinazolinyl and quinoxalinyl, each of which is optionally further substituted by one or more substituents selected from alkyl, halo and haloalkyl. In one preferred embodiment, R² is a pyrimidinyl group substituted by one or more - NR¹⁶R¹⁷ groups.

In one preferred embodiment, R² is a pyrimidin-5-yl group substituted in the 2-position by an -NR¹⁶R¹⁷ group.

In one preferred embodiment, R² is a pyrazolyl group substituted by one or more

-(CH₂)_nR¹⁷ groups, wherein n is preferably zero, and R¹⁷ is -(CHR¹⁰)_n-heteroaryl, wherein said heteroaryi group is selected from a pyridinyl group and a pyrazinyl group, each of which in turn is optionally substituted by one or more R⁷ groups. in one preferred embodiment, R¹ is -NR³R⁴, R³ is H and R⁴ is:

(i) cyclohexyl substituted by one or more groups selected from -NR¹¹R¹², and - NHCOR¹¹;

(ii) ~(CH₂)_n-heterocycloalkyl, wherein said heterocycloalkyl is a piperidinyl, pyrrolidinyl or azetidinyl group, each of which is optionally substituted by one or more (CH₂)_nR⁷ groups; or

(iii) alkyl substituted by one or more -NR ¹R¹² groups; or

R³ and R⁴ are linked together with the nitrogen to which they are attached to form a piperidinyl group or an azetidinyl group each of which is optionally substituted by one or more R⁷ groups.

In one preferred embodiment, R¹ is -NR³R⁴, R³ is H and R⁴ is selected from the following:

In one preferred embodiment, R¹ is -NR³R⁴, R³ is H and R⁴ is:

In one preferred embodiment, R¹ is -NR³R⁴, and R³and R⁴ are linked together such that R¹ is selected from the following:

In one preferred embodiment, R¹ is OR⁵ and R⁵ is selected from the following

In one preferred embodiment, R¹ is a group selected from the following:

In another preferred embodiment R is a group selected from the following:

In one preferred embodiment, the compound of the invention is of formula la, or a pharmaceutically acceptable salt or ester thereof

(la)

wherein:

R¹ is -NR³R⁴ or -OR⁵;

R² is selected from pyrimidinyl, pyridinyl, phenyl, indolyl, indazolyl, pyrazolyl, pyrazolopyridinyl, benzimidazolyl and fused aryl-heterocycloalkyl, each of which is substituted by at least one R⁸ group, and optionally further substituted by one or more R⁷ groups, and wherein said heterocycloalkyl is a 5 or 6-membered nitrogen-containing group optionally containing one or more CO groups;

R³ is H or alkyl;

R⁴ is:

(i) cycloalkyl substituted by one or more -NR¹¹R¹² and -NHCOR groups; or

(ii) heterocycloalkyl, wherein said heterocycloalkyl is a 4, 5 or 6-membered nitrogen- containing group optionally containing one or more CO groups, wherein said heterocycloalkyl is optionally substituted by one or more groups selected from alkyl and hydroxyalkyl; or

R³ and R⁴ are linked together with the nitrogen to which they are attached to form a 4, 5 or 6-membered heterocycloalkyl group optionally containing one or two further groups selected from CO, O and S, and which is substituted by one or more groups selected from NR¹¹R¹² and C0₂R¹¹;

R⁵ is selected from alkyl, -(CH₂)_n-heteroaryl and -(CH₂)_n-heterocycloalkyI, wherein said heteroaryl and heterocycloalkyl groups are each optionally substituted by one or more R⁷ groups;

each R⁷ is independently selected from -NR¹¹R¹², halo, CN, nitro, -COR¹¹, -CONR¹¹R¹², alkyl, haloalkyl, haloalkoxy, -OR¹¹, -NHC0₂R¹¹, -NHCOR ¹, -NHS0₂R¹¹ and -C0₂R¹¹;

each R⁸ is independently selected from -NR¹⁶R¹⁷and OR¹⁷, where each R¹⁶ is H and each R¹⁷ is independently -(CHR¹⁰)_n-heteroaryl, wherein said heteroaryl group is in turn optionally substituted by one or more R⁷ groups;

each R ¹ and R¹² is independently H or alkyl; and

each n is independently an integer from 0 to 6.

In another preferred embodiment, the compound of the invention is of formula lb, or a pharmaceutically acceptable salt or ester thereof

(lb)

wherein:

R¹ is -NR³R⁴ or -OR⁵;

R² is selected from pyrimidinyl, pyridinyl and phenyl, each of which is substituted by at least one R⁸ group, and optionally further substituted by one or more R⁷ groups;

R³ is H or alkyl;

R⁴ is:

(i) -(CH₂)_m-piperidinyl, -(CH₂)_m-(2-pyrrolidon-1-yl), wherein said piperidinyl or 2- pyrrolidon-1-yl group is optionally substituted by one or more one or more (CH₂)_nR⁷ groups; or

(ii) alkyl substituted by one or more -NR¹¹R¹²groups; R⁵ is selected from alkyl, -(CH₂)_n-heteroaryl and -(CH₂)_n-heterocycloalkyl, wherein said heteroaryl and heterocycloalkyi groups are each optionally substituted by one or more R⁷ groups;

each R⁷ is independently selected from -NR¹¹R¹², halo, CN, nitro, -COR¹¹, -CONR¹¹R¹², alkyl, haloalkyl, haloalkoxy, -OR¹¹, -NHC0₂R¹¹, -NHCOR , -NHS0₂R¹¹ and -C0₂R¹¹;

each R^s is independently selected from -NR ⁶R¹⁷ and OR¹⁷, where each R ⁶ is H and each R¹⁷ is independently -(CHR¹⁰)_n-heteroaryl, wherein said heteroaryl group is in turn optionally substituted by one or more R⁷ groups;

each R ¹ and R¹² is independently H or alkyl;

each m is independently an integer from 1 to 6; and

each n is independently an integer from 0 to 6.

In one highly preferred embodiment, the compound of the invention is selected from the following:

and pharmaceutically acceptable salts thereof.

Preferably, the compound of the invention is capable of inhibiting a CDPK, more preferably, CDPK1 , even more preferably, PfCDPKI .

In one preferred embodiment, the compound of the invention exhibits an IC_S0 value against PfCDPKI of from about 1 μΜ to about 10 μΜ. In another preferred embodiment, the compound of the invention exhibits an IC₅₀ value against PfCDPKI of from about 500 to about 1000 nM.

In another preferred embodiment, the compound of the invention exhibits an IC_5D value against PfCDPKI of from about 100 nM to about 500 nM. In one highly preferred embodiment, the compound of the invention exhibits an IC_5D value against PfCDPKI of less than about 100 nM. THERAPEUTIC APPLICATIONS

Another aspect of the invention relates to a compound as described above for use in treating or preventing malaria

Another aspect relates to the use of a compound as described above in the preparation of a medicament for treating or preventing malaria.

Preferably, the compound is administered in an amount sufficient to inhibit CDPK, more preferably, in an amount sufficient to inhibit CDPK1 , more preferably still, PfCDPKI . Another aspect of the invention relates to a compound as described above for use in treating or preventing a CDPK1 -related disease or disorder. Preferably, the CDPK1- related disease or disorder is malaria.

Another aspect of the invention relates to a method of treating a CDPK1 -related disease or disorder. The method according to this aspect of the present invention is effected by administering to a subject in need thereof a therapeutically effective amount of a compound of the present invention, as described hereinabove, either per se, or, more preferably, as a part of a pharmaceutical composition, mixed with, for example, a pharmaceutically acceptable carrier, as is detailed hereinafter.

Yet another aspect of the invention relates to a method of treating a mammal having a disease state alleviated by the inhibition of CDPK1 , wherein the method comprises administering to a mammal a therapeutically effective amount of a compound according to the invention.

Preferably, the mammal is a human. Yet another aspect of the invention relates to the use of a compound of the invention in the preparation of a medicament for the prevention or treatment of a disorder caused by, associated with or accompanied by abnormal PfCDPKI activity. As used herein, the term "method" refers to manners, means, techniques and procedures for accomplishing a given task including, but not limited to, those manners, means, techniques and procedures either known to, or readily developed from known manners, means, techniques and procedures by practitioners of the chemical, pharmacological, biological, biochemical and medical arts.

The term "administering" as used herein refers to a method for bringing a compound of the present invention and a target kinase together in such a manner that the compound can affect the enzyme activity of the kinase either directly; i.e., by interacting with the kinase itself or indirectly; i.e., by interacting with another molecule on which the catalytic activity of the kinase is dependent. As used herein, administration can be accomplished either in vitro, i.e. in a test tube, or in vivo, i.e., in cells or tissues of a living organism.

Herein, the term "treating" includes abrogating, substantially inhibiting, slowing or reversing the progression of a disease or disorder, substantially ameliorating clinical symptoms of a disease or disorder or substantially preventing the appearance of clinical symptoms of a disease or disorder.

Herein, the term "preventing" refers to a method for barring an organism from acquiring a disorder or disease in the first place.

The term "therapeutically effective amount" refers to that amount of the compound being administered which will relieve to some extent one or more of the symptoms of the disease or disorder being treated. For any compound used in this invention, a therapeutically effective amount, also referred to herein as a therapeutically effective dose, can be estimated initially from cell culture assays. For example, a dose can be formulated in animal models to achieve a circulating concentration range that includes the IC_5D or the IC₁₀₀ as determined in cell culture. Such information can be used to more accurately determine useful doses in humans. Initial dosages can also be estimated from in vivo data. Using these initial guidelines one of ordinary skill in the art could determine an effective dosage in humans.

Moreover, toxicity and therapeutic efficacy of the compounds described herein can be determined by standard pharmaceutical procedures in cell cultures or experimental animals, e.g., by determining the LD₅₀ and the ED₅₀. The dose ratio between toxic and therapeutic effect is the therapeutic index and can be expressed as the ratio between LD_5D and ED₅₀. Compounds which exhibit high therapeutic indices are preferred. The data obtained from these cell cultures assays and animal studies can be used in formulating a dosage range that is not toxic for use in human. The dosage of such compounds lies preferably within a range of circulating concentrations that include the ED₅₀with little or no toxicity. The dosage may vary within this range depending upon the dosage form employed and the route of administration utilized. The exact formulation, route of administration and dosage can be chosen by the individual physician in view of the patient's condition, (see, e.g., Fingl et al., 1975, In: The Pharmacological Basis of Therapeutics, chapter 1 , page 1). Dosage amount and interval may be adjusted individually to provide plasma levels of the active compound which are sufficient to maintain therapeutic effect. Usual patient dosages for oral administration range from about 50-2000 mg/kg/day, commonly from about 100- 1000 mg/kg/day, preferably from about 150-700 mg/kg/day and most preferably from about 250-500 mg/kg/day. Preferably, therapeutically effective serum levels will be achieved by administering multiple doses each day. In cases of local administration or selective uptake, the effective local concentration of the drug may not be related to plasma concentration. One skilled in the art will be able to optimize therapeutically effective local dosages without undue experimentation.

As used herein, "CDPK1 -related disease or disorder" refers to a disease or disorder characterized by inappropriate CDPK1 activity, for example, diseases or disorders characterised by ectopic CDPK1 activity, or where it is desirable to inhibit CDPK1 activity. Preferred CDPK1 related diseases or disorders that the compounds described herein may be useful in preventing, treating and/or studying include malaria.

The present invention further relates to the use of compounds as defined herein for the manufacture of medicaments for the treatment of diseases where it is desirable to inhibit CDPK1 , more preferably PfCDPKI . Such diseases include malaria.

In a further aspect there is provided a method of treating or preventing malaria in a subject, said method comprising the step of administering to the subject an effective amount of a compound of the invention.

PHARMACEUTICAL COMPOSTIONS

For use according to the present invention, the compounds or physiologically acceptable salt, ester or other physiologically functional derivative thereof, described herein, may be presented as a pharmaceutical formulation, comprising the compounds or physiologically acceptable salt, ester or other physiologically functional derivative thereof, together with one or more pharmaceutically acceptable carriers therefore and optionally other therapeutic and/or prophylactic ingredients. The carrier(s) must be acceptable in the sense of being compatible with the other ingredients of the formulation and not deleterious to the recipient thereof. The pharmaceutical compositions may be for human or animal usage in human and veterinary medicine.

Examples of such suitable excipients for the various different forms of pharmaceutical compositions described herein may be found in the "Handbook of Pharmaceutical Excipients, 2^nd Edition, (1994), Edited by A Wade and PJ Weller.

Acceptable carriers or diluents for therapeutic use are well known in the pharmaceutical art, and are described, for example, in Remington's Pharmaceutical Sciences, Mack Publishing Co. (A. R. Gennaro edit. 1985). Examples of suitable carriers include lactose, starch, glucose, methyl cellulose, magnesium stearate, mannitol, sorbitol and the like. Examples of suitable diluents include ethanol, glycerol and water. The choice of pharmaceutical carrier, excipient or diluent can be selected with regard to the intended route of administration and standard pharmaceutical practice. The pharmaceutical compositions may comprise as, or in addition to, the carrier, excipient or diluent any suitable binder(s), lubricant(s), suspending agent(s), coating agent(s), solubilising agent(s), buffer(s), flavouring agent(s), surface active agent(s), thickener(s), preservative(s) (including anti-oxidants) and the like, and substances included for the purpose of rendering the formulation isotonic with the blood of the intended recipient.

Examples of suitable binders include starch, gelatin, natural sugars such as glucose, anhydrous lactose, free-flow lactose, beta-lactose, corn sweeteners, natural and synthetic gums, such as acacia, tragacanth or sodium alginate, carboxymethyl cellulose and polyethylene glycol.

Examples of suitable lubricants include sodium oleate, sodium stearate, magnesium stearate, sodium benzoate, sodium acetate, sodium chloride and the like.

Preservatives, stabilizers, dyes and even flavoring agents may be provided in the pharmaceutical composition. Examples of preservatives include sodium benzoate, sorbic acid and esters of p-hydroxybenzoic acid. Antioxidants and suspending agents may be also used. Pharmaceutical formulations include those suitable for oral, topical (including dermal, buccal and sublingual), rectal or parenteral (including subcutaneous, intradermal, intramuscular and intravenous), nasal and pulmonary administration e.g., by inhalation. The formulation may, where appropriate, be conveniently presented in discrete dosage units and may be prepared by any of the methods well known in the art of pharmacy. All methods include the step of bringing into association an active compound with liquid carriers or finely divided solid carriers or both and then, if necessary, shaping the product into the desired formulation. Pharmaceutical formulations suitable for oral administration wherein the carrier is a solid are most preferably presented as unit dose formulations such as boluses, capsules or tablets each containing a predetermined amount of active compound. A tablet may be made by compression or moulding, optionally with one or more accessory ingredients. Compressed tablets may be prepared by compressing in a suitable machine an active compound in a free-flowing form such as a powder or granules optionally mixed with a binder, lubricant, inert diluent, lubricating agent, surface-active agent or dispersing agent. Moulded tablets may be made by moulding an active compound with an inert liquid diluent. Tablets may be optionally coated and, if uncoated, may optionally be scored. Capsules may be prepared by filling an active compound, either alone or in admixture with one or more accessory ingredients, into the capsule shells and then sealing them in the usual manner. Cachets are analogous to capsules wherein an active compound together with any accessory ingredient(s) is sealed in a rice paper envelope. An active compound may also be formulated as dispersible granules, which may for example be suspended in water before administration, or sprinkled on food. The granules may be packaged, e.g., in a sachet. Formulations suitable for oral administration wherein the carrier is a liquid may be presented as a solution or a suspension in an aqueous or non-aqueous liquid, or as an oil- in-water liquid emulsion. Formulations for oral administration include controlled release dosage forms, e.g., tablets wherein an active compound is formulated in an appropriate release - controlling matrix, or is coated with a suitable release - controlling film. Such formulations may be particularly convenient for prophylactic use. Pharmaceutical formulations suitable for rectal administration wherein the carrier is a solid are most preferably presented as unit dose suppositories. Suitable carriers include cocoa butter and other materials commonly used in the art. The suppositories may be conveniently formed by admixture of an active compound with the softened or melted carrier(s) followed by chilling and shaping in moulds.

Pharmaceutical formulations suitable for parenteral administration include sterile solutions or suspensions of an active compound in aqueous or oleaginous vehicles. Injectible preparations may be adapted for bolus injection or continuous infusion. Such preparations are conveniently presented in unit dose or multi-dose containers which are sealed after introduction of the formulation until required for use. Alternatively, an active compound may be in powder form which is constituted with a suitable vehicle, such as sterile, pyrogen-free water, before use.

An active compound may also be formulated as long-acting depot preparations, which may be administered by intramuscular injection or by implantation, e.g., subcutaneously or intramuscularly. Depot preparations may include, for example, suitable polymeric or hydrophobic materials, or ion-exchange resins. Such long-acting formulations are particularly convenient for prophylactic use.

Formulations suitable for pulmonary administration via the buccal cavity are presented such that particles containing an active compound and desirably having a diameter in the range of 0.5 to 7 microns are delivered in the bronchial tree of the recipient. As one possibility such formulations are in the form of finely comminuted powders which may conveniently be presented either in a pierceable capsule, suitably of, for example, gelatin, for use in an inhalation device, or alternatively as a self-propelling formulation comprising an active compound, a suitable liquid or gaseous propellant and optionally other ingredients such as a surfactant and/or a solid diluent. Suitable liquid propellants include propane and the chlorofluorocarbons, and suitable gaseous propellants include carbon dioxide. Self-propelling formulations may also be employed wherein an active compound is dispensed in the form of droplets of solution or suspension. Such self-propelling formulations are analogous to those known in the art and may be prepared by established procedures. Suitably they are presented in a container provided with either a manually-operable or automatically functioning valve having the desired spray characteristics; advantageously the valve is of a metered type delivering a fixed volume, for example, 25 to 100 microlitres, upon each operation thereof. As a further possibility an active compound may be in the form of a solution or suspension for use in an atomizer or nebuliser whereby an accelerated airstream or ultrasonic agitation is employed to produce a fine droplet mist for inhalation. Formulations suitable for nasal administration include preparations generally similar to those described above for pulmonary administration. When dispensed such formulations should desirably have a particle diameter in the range 10 to 200 microns to enable retention in the nasal cavity; this may be achieved by, as appropriate, use of a powder of a suitable particle size or choice of an appropriate valve. Other suitable formulations include coarse powders having a particle diameter in the range 20 to 500 microns, for administration by rapid inhalation through the nasal passage from a container held close up to the nose, and nasal drops comprising 0.2 to 5% w/v of an active compound in aqueous or oily solution or suspension. Pharmaceutically acceptable carriers are well known to those skilled in the art and include, but are not limited to, 0.1 M and preferably 0.05 M phosphate buffer or 0.8% saline. Additionally, such pharmaceutically acceptable carriers may be aqueous or non-aqueous solutions, suspensions, and emulsions. Examples of non-aqueous solvents are propylene glycol, polyethylene glycol, vegetable oils such as olive oil, and injectable organic esters such as ethyl oleate. Aqueous carriers include water, alcoholic/aqueous solutions, emulsions or suspensions, including saline and buffered media. Parenteral vehicles include sodium chloride solution, Ringer's dextrose, dextrose and sodium chloride, lactated Ringer's or fixed oils. Preservatives and other additives may also be present, such as, for example, antimicrobials, antioxidants, chelating agents, inert gases and the like.

Formulations suitable for topical formulation may be provided for example as gels, creams or ointments. Such preparations may be applied to the site to be treated, or carried on a suitable support such as a bandage, gauze, mesh or the like which may be applied to and over the area to be treated.

Liquid or powder formulations may also be provided which can be sprayed or sprinkled directly onto the site to be treated. Alternatively, a carrier such as a bandage, gauze, mesh or the like can be sprayed or sprinkle with the formulation and then applied to the site to be treated.

According to a further aspect of the invention, there is provided a process for the preparation of a pharmaceutical or veterinary composition as described above, the process comprising bringing the active compound(s) into association with the carrier, for example by admixture.

In general, the formulations are prepared by uniformly and intimately bringing into association the active agent with liquid carriers or finely divided solid carriers or both, and then if necessary shaping the product. The invention extends to methods for preparing a pharmaceutical composition comprising bringing a compound of general formula (I) in conjunction or association with a pharmaceutically or veterinarily acceptable carrier or vehicle.

SALTS/ESTERS

The compounds of the invention can be present as salts or esters, in particular pharmaceutically and veterinarily acceptable salts or esters. Pharmaceutically acceptable salts of the compounds of the invention include suitable acid addition or base salts thereof. A review of suitable pharmaceutical salts may be found in Berge et al, J Pharm Sci, 66, 1-19 (1977). Salts are formed, for example with strong inorganic acids such as mineral acids, e.g. hydrohalic acids such as hydrochloride, hydrobromide and hydroiodide, sulfuric acid, phosphoric acid sulphate, bisulphate, hemisulphate, thiocyanate, persulphate and sulphonic acids; with strong organic carboxylic acids, such as alkanecarboxylic acids of 1 to 4 carbon atoms which are unsubstituted or substituted (e.g., by halogen), such as acetic acid; with saturated or unsaturated dicarboxylic acids, for example oxalic, malonic, succinic, maleic, fumaric, phthalic or tetraphthalic; with hydroxycarboxylic acids, for example ascorbic, glycolic, lactic, malic, tartaric or citric acid; with aminoacids, for example aspartic or glutamic acid; with benzoic acid; or with organic sulfonic acids, such as (CVC₄)-alkyl- or aryl-sulfonic acids which are unsubstituted or substituted (for example, by a halogen) such as methane- or p-toluene sulfonic acid. Salts which are not pharmaceutically or veterinarily acceptable may still be valuable as intermediates. Preferred salts include, for example, acetate, trifluoroacetate, lactate, gluconate, citrate, tartrate, maleate, malate, pantothenate, adipate, alginate, aspartate, benzoate, butyrate, digluconate, cyclopentanate, glucoheptanate, glycerophosphate, oxalate, heptanoate, hexanoate, fumarate, nicotinate, palmoate, pectinate, 3-phenylpropionate, picrate, pivalate, proprionate, tartrate, lactobionate, pivolate, camphorate, undecanoate and succinate, organic sulphonic acids such as methanesulphonate, ethanesulphonate, 2-hydroxyethane sulphonate, camphorsulphonate, 2-naphthalenesulphonate, benzenesulphonate, p- chlorobenzenesulphonate and p-toluenesulphonate; and inorganic acids such as hydrochloride, hydrobromide, hydroiodide, sulphate, bisulphate, hemisulphate, thiocyanate, persulphate, phosphoric and sulphonic acids.

Esters are formed either using organic acids or alcohols/hydroxides, depending on the functional group being esterified. Organic acids include carboxylic acids, such as alkanecarboxylic acids of 1 to 12 carbon atoms which are unsubstituted or substituted (e.g., by halogen), such as acetic acid; with saturated or unsaturated dicarboxylic acid, for example oxalic, malonic, succinic, maleic, fumaric, phthalic or tetraphthalic; with hydroxycarboxylic acids, for example ascorbic, glycolic, lactic, malic, tartaric or citric acid; with aminoacids, for example aspartic or glutamic acid; with benzoic acid; or with organic sulfonic acids, such as (d-C^-alkyl- or aryl-sulfonic acids which are unsubstituted or substituted (for example, by a halogen) such as methane- or p-toluene sulfonic acid. Suitable hydroxides include inorganic hydroxides, such as sodium hydroxide, potassium hydroxide, calcium hydroxide, aluminium hydroxide. Alcohols include alkanealcohols of 1- 12 carbon atoms which may be unsubstituted or substituted, e.g. by a halogen).

ENANTIOMERS/TAUTO ERS

In all aspects of the present invention previously discussed, the invention includes, where appropriate all enantiomers, diastereoisomers and tautomers of the compounds of the invention. The person skilled in the art will recognise compounds that possess optical properties (one or more chiral carbon atoms) or tautomeric characteristics. The corresponding enantiomers and/or tautomers may be isolated/prepared by methods known in the art. Enantiomers are characterised by the absolute configuration of their chiral centres and described by the R- and S-sequencing rules of Cahn, Ingold and Prelog. Such conventions are well known in the art (e.g. see 'Advanced Organic Chemistry', 3^rd edition, ed. March, J., John Wiley and Sons, New York, 1985).

Compounds of the invention containing a chiral centre may be used as a racemic mixture, an enantiomerically enriched mixture, or the racemic mixture may be separated using well- known techniques and an individual enantiomer may be used alone.

STEREO AND GEOMETRIC ISOMERS

Some of the compounds of the invention may exist as stereoisomers and/or geometric isomers - e.g. they may possess one or more asymmetric and/or geometric centres and so may exist in two or more stereoisomeric and/or geometric forms. The present invention contemplates the use of all the individual stereoisomers and geometric isomers of those inhibitor agents, and mixtures thereof. The terms used in the claims encompass these forms, provided said forms retain the appropriate functional activity (though not necessarily to the same degree).

The present invention also includes all suitable isotopic variations of the agent or a pharmaceutically acceptable salt thereof. An isotopic variation of an agent of the present invention or a pharmaceutically acceptable salt thereof is defined as one in which at least one atom is replaced by an atom having the same atomic number but an atomic mass different from the atomic mass usually found in nature. Examples of isotopes that can be incorporated into the agent and pharmaceutically acceptable salts thereof include isotopes of hydrogen, carbon, nitrogen, oxygen, phosphorus, sulfur, fluorine and chlorine such as ²H, ³H, ¹³C, ¹⁴C, ¹⁵N, ¹⁷0, ¹⁸0, ³¹P, ³²P, ³⁵S, ¹⁸F and ³⁶CI, respectively. Certain isotopic variations of the agent and pharmaceutically acceptable salts thereof, for example, those in which a radioactive isotope such as ³H or ¹⁴C is incorporated, are useful in drug and/or substrate tissue distribution studies. Tritiated, i.e., ³H, and carbon-14, i.e., ¹ C, isotopes are particularly preferred for their ease of preparation and detectability. Further, substitution with isotopes such as deuterium, i.e., ²H, may afford certain therapeutic advantages resulting from greater metabolic stability, for example, increased in vivo half-life or reduced dosage requirements and hence may be preferred in some circumstances. For example, the invention includes compounds of general formula (I) where any hydrogen atom has been replaced by a deuterium atom. Isotopic variations of the agent of the present invention and pharmaceutically acceptable salts thereof of this invention can generally be prepared by conventional procedures using appropriate isotopic variations of suitable reagents.

PRODRUGS

The invention further includes the compounds of the present invention in prodrug form, i.e. covalently bonded compounds which release the active parent drug according to general formula (I) in vivo. Such prodrugs are generally compounds of the invention wherein one or more appropriate groups have been modified such that the modification may be reversed upon administration to a human or mammalian subject. Reversion is usually performed by an enzyme naturally present in such subject, though it is possible for a second agent to be administered together with such a prodrug in order to perform the reversion in vivo. Examples of such modifications include ester (for example, any of those described above), wherein the reversion may be carried out be an esterase etc. Other such systems will be well known to those skilled in the art.

SOLVATES

The present invention also includes solvate forms of the compounds of the present invention. The terms used in the claims encompass these forms.

POLYMORPHS

The invention further relates to the compounds of the present invention in their various crystalline forms, polymorphic forms and (an)hydrous forms. It is well established within the pharmaceutical industry that chemical compounds may be isolated in any of such forms by slightly varying the method of purification and or isolation form the solvents used in the synthetic preparation of such compounds. ADMINISTRATION

The pharmaceutical compositions of the present invention may be adapted for rectal, nasal, intrabronchial, topical (including buccal and sublingual), vaginal or parenteral (including subcutaneous, intramuscular, intravenous, intraarterial and intradermal), intraperitoneal or intrathecal administration. Preferably the formulation is an orally administered formulation. The formulations may conveniently be presented in unit dosage form, i.e., in the form of discrete portions containing a unit dose, or a multiple or sub-unit of a unit dose. By way of example, the formulations may be in the form of tablets and sustained release capsules, and may be prepared by any method well known in the art of pharmacy.

Formulations for oral administration in the present invention may be presented as: discrete units such as capsules, gellules, drops, cachets, pills or tablets each containing a predetermined amount of the active agent; as a powder or granules; as a solution, emulsion or a suspension of the active agent in an aqueous liquid or a non-aqueous liquid; or as an oil-in-water liquid emulsion or a water-in-oil liquid emulsion; or as a bolus etc. Preferably, these compositions contain from 1 to 250 mg and more preferably from 10-100 mg, of active ingredient per dose. For compositions for oral administration (e.g. tablets and capsules), the term "acceptable carrier" includes vehicles such as common excipients e.g. binding agents, for example syrup, acacia, gelatin, sorbitol, tragacanth, polyvinylpyrrolidone (Povidone), methylcellulose, ethylcellulose, sodium carboxymethylcellulose, hydroxypropyl-methylcellulose, sucrose and starch; fillers and carriers, for example corn starch, gelatin, lactose, sucrose, microcrystalline cellulose, kaolin, mannitol, dicalcium phosphate, sodium chloride and alginic acid; and lubricants such as magnesium stearate, sodium stearate and other metallic stearates, glycerol stearate stearic acid, silicone fluid, talc waxes, oils and colloidal silica. Flavouring agents such as peppermint, oil of wintergreen, cherry flavouring and the like can also be used. It may be desirable to add a colouring agent to make the dosage form readily identifiable. Tablets may also be coated by methods well known in the art. A tablet may be made by compression or moulding, optionally with one or more accessory ingredients. Compressed tablets may be prepared by compressing in a suitable machine the active agent in a free flowing form such as a powder or granules, optionally mixed with a binder, lubricant, inert diluent, preservative, surface-active or dispersing agent. Moulded tablets may be made by moulding in a suitable machine a mixture of the powdered compound moistened with an inert liquid diluent. The tablets may be optionally be coated or scored and may be formulated so as to provide slow or controlled release of the active agent. Other formulations suitable for oral administration include lozenges comprising the active agent in a flavoured base, usually sucrose and acacia or tragacanth; pastilles comprising the active agent in an inert base such as gelatin and glycerin, or sucrose and acacia; and mouthwashes comprising the active agent in a suitable liquid carrier. Other forms of administration comprise solutions or emulsions which may be injected intravenously, intraarterially, intrathecally, subcutaneously, intradermally, intraperitoneally or intramuscularly, and which are prepared from sterile or sterilisable solutions. Injectable forms typically contain between 10 - 1000 mg, preferably between 10 - 250 mg, of active ingredient per dose.

The pharmaceutical compositions of the present invention may also be in form of suppositories, pessaries, suspensions, emulsions, lotions, ointments, creams, gels, sprays, solutions or dusting powders. An alternative means of transdermal administration is by use of a skin patch. For example, the active ingredient can be incorporated into a cream consisting of an aqueous emulsion of polyethylene glycols or liquid paraffin. The active ingredient can also be incorporated, at a concentration of between 1 and 10% by weight, into an ointment consisting of a white wax or white soft paraffin base together with such stabilisers and preservatives as may be required. DOSAGE

A person of ordinary skill in the art can easily determine an appropriate dose of one of the instant compositions to administer to a subject without undue experimentation. Typically, a physician will determine the actual dosage which will be most suitable for an individual patient and it will depend on a variety of factors including the activity of the specific compound employed, the metabolic stability and length of action of that compound, the age, body weight, general health, sex, diet, mode and time of administration, rate of excretion, drug combination, the severity of the particular condition, and the individual undergoing therapy. The dosages disclosed herein are exemplary of the average case. There can of course be individual instances where higher or lower dosage ranges are merited, and such are within the scope of this invention.

In accordance with this invention, an effective amount of a compound of general formula (I) may be administered to inhibit the CDPK implicated with a particular condition or disease. Of course, this dosage amount will further be modified according to the type of administration of the compound. For example, to achieve an "effective amount" for acute therapy, parenteral administration of a compound of general formula (I) is preferred. An intravenous infusion of the compound in 5% dextrose in water or normal saline, or a similar formulation with suitable excipients, is most effective, although an intramuscular bolus injection is also useful. Typically, the parenteral dose will be about 0.01 to about 100 mg/kg; preferably between 0.1 and 20 mg/kg, in a manner to maintain the concentration of drug in the plasma at a concentration effective to inhibit a CDPK. The compounds may be administered one to four times daily at a level to achieve a total daily dose of about 0.4 to about 400 mg/kg/day. The precise amount of an inventive compound which is therapeutically effective, and the route by which such compound is best administered, is readily determined by one of ordinary skill in the art by comparing the blood level of the agent to the concentration required to have a therapeutic effect.

The compounds of this invention may also be administered orally to the patient, in a manner such that the concentration of drug is sufficient to achieve one or more of the therapeutic indications disclosed herein. Typically, a pharmaceutical composition containing the compound is administered at an oral dose of between about 0.1 to about 50 mg/kg in a manner consistent with the condition of the patient. Preferably the oral dose would be about 0.5 to about 20 mg/kg.

No unacceptable toxicological effects are expected when compounds of the present invention are administered in accordance with the present invention. The compounds of this invention, which may have good bioavailability, may be tested in one of several biological assays to determine the concentration of a compound which is required to have a given pharmacological effect. COMBINATIONS

In a particularly preferred embodiment, the one or more compounds of the invention are administered in combination with one or more other active agents, for example, existing drugs available on the market. In such cases, the compounds of the invention may be administered consecutively, simultaneously or sequentially with the one or more other active agents.

Drugs in general are more effective when used in combination. In particular, combination therapy is desirable in order to avoid an overlap of major toxicities, mechanism of action and resistance mechanism(s). Furthermore, it is also desirable to administer most drugs at their maximum tolerated doses with minimum time intervals between such doses. The major advantages of combining chemotherapeutic drugs are that it may promote additive or possible synergistic effects through biochemical interactions and also may decrease the emergence of resistance. Beneficial combinations may be suggested by studying the inhibitory activity of the test compounds with agents known or suspected of being valuable in the treatment of a particular disorder. This procedure can also be used to determine the order of administration of the agents, i.e. before, simultaneously, or after delivery. Such scheduling may be a feature of all the active agents identified herein. ASSAY

A further aspect of the invention relates to the use of a compound of formula I as described above in an assay for identifying further candidate compounds capable of inhibiting a CDPK, more preferably, CDPK1 , more preferably still, PfCDPKL

Preferably, the assay is a competitive binding assay.

More preferably, the competitive binding assay comprises contacting a compound of the invention with CDPK1 and a candidate compound and detecting any change in the interaction between the compound according to the invention and the CDPK1.

Preferably, the candidate compound is generated by conventional SAR modification of a compound of the invention. As used herein, the term "conventional SAR modification" refers to standard methods known in the art for varying a given compound by way of chemical derivatisation.

Thus, in one aspect, the identified compound may act as a model (for example, a template) for the development of other compounds. The compounds employed in such a test may be free in solution, affixed to a solid support, borne on a cell surface, or located intracellularly. The abolition of activity or the formation of binding complexes between the compound and the agent being tested may be measured.

The assay of the present invention may be a screen, whereby a number of agents are tested. In one aspect, the assay method of the present invention is a high through-put screen.

This invention also contemplates the use of competitive drug screening assays in which neutralising antibodies capable of binding a compound specifically compete with a test compound for binding to a compound. Another technique for screening provides for high throughput screening (HTS) of agents having suitable binding affinity to the substances and is based upon the method described in detail in WO 84/03564. It is expected that the assay methods of the present invention will be suitable for both small and large-scale screening of test compounds as well as in quantitative assays.

Preferably, the competitive binding assay comprises contacting a compound of the invention with a CDPK1 in the presence of a known substrate of said CDPK1 and detecting any change in the interaction between said kinase and said known substrate.

A further aspect of the invention provides a method of detecting the binding of a ligand to a kinase, said method comprising the steps of:

(i) contacting a ligand with a CDPK1 in the presence of a known substrate of said CDPK1 ;

(ii) detecting any change in the interaction between said CDPK1 and said known substrate;

and wherein said ligand is a compound of the invention. One aspect of the invention relates to a process comprising the steps of:

(a) performing an assay method described hereinabove;

(b) identifying one or more ligands capable of binding to a ligand binding domain; and

(c) preparing a quantity of said one or more ligands. Another aspect of the invention provides a process comprising the steps of:

(a) performing an assay method described hereinabove;

(c) preparing a pharmaceutical composition comprising said one or more ligands. Another aspect of the invention provides a process comprising the steps of: (a) performing an assay method described hereinabove;

(b) identifying one or more ligands capable of binding to a ligand binding domain;

(c) modifying said one or more ligands capable of binding to a ligand binding domain;

(d) performing the assay method described hereinabove;

(e) optionally preparing a pharmaceutical composition comprising said one or more ligands.

The invention also relates to a ligand identified by the method described hereinabove. Yet another aspect of the invention relates to a pharmaceutical composition comprising a ligand identified by the method described hereinabove.

Another aspect of the invention relates to the use of a ligand identified by the method described hereinabove in the preparation of a pharmaceutical composition for use in the treatment of malaria.

The above methods may be used to screen for a ligand useful as an inhibitor of one or more CDPKs. Compounds, of general formula (I) are useful both as laboratory tools and as therapeutic agents. In the laboratory certain compounds of the invention are useful in establishing whether a known or newly discovered kinase contributes a critical or at least significant biochemical function during the establishment or progression of a disease state, a process commonly referred to as 'target validation'.

PROCESS

A further aspect of the invention relates to a process for preparing a compound as described above. Further details of synthetic routes may be found in the accompanying examples section. One aspect of the invention relates to a process for preparing a compound of formula (Ic), wherein R¹ is -NR³R⁴ or -OR⁵ and R² is as defined above, said process comprising the steps of:

(i) reacting a compound of formula (II) with a compound of formula HNR³R⁴ or HOR⁵ to form an intermediate compound of formula (III);

(ii) converting said intermediate compound of formula (III) to a compound of formula (I).

Preferably, the compound of formula (III) is coupled to a compound of formula R²'H, wherein R²' is a precursor to the group R². More preferably, the coupling reaction is a palladium catalysed coupling reaction. After coupling, the group R²' is modified to incorporate one or more R⁸ groups.

The present invention is further described by way of the following non-limiting examples.

EXAMPLES

Genera! procedures for synthesis of compounds

Chromatography

Preparative high pressure liquid chromatography was carried out using apparatus made by Agilent. The apparatus is constructed such that the chromatography (column: either a 19x100mm (5ym) C-18 Waters Xbridge or a 19x100mm (5μηι) C-6Ph Waters Xbridge column, both at a flow rate of 40 mUmin) is monitored by a multi-wavelength UV detector (G1365B manufactured by Agilent) and an MM-ES+APCI mass spectrometer (G-1956A, manufactured by Agilent) connected in series, and if the appropriate criteria are met the sample is collected by an automated fraction collector (G1364B manufactured by Agilent). Collection can be triggered by any combination of UV or mass spectrometry or can be based on time. Typical conditions for the separation process are as follows: The gradient is run over a 7 minute period (gradient at start: 10% methanol and 90% water, gradient at finish: 100% methanol and 0% water; as buffer: either 0.1 % formic acid, 0.1 %» ammonium hydroxide or 0.1 % trifluoroacetic acid is added to the water). It will be appreciated by those skilled in the art that it may be necessary or desirable to modify the conditions for each specific compound, for example by changing the solvent composition at the start or at the end, modifying the solvents or buffers, changing the run time, changing the flow rate and/or the chromatography column. Column chromatography refers to silica gel chromatography and carried out using an SP4 MPLC system (manufactured by Biotage); pre-packed silica gel cartridges (supplied by Biotage); or using conventional glass column chromatography.

Analytical Methods

1H Nuclear magnetic resonance (NMR) spectroscopy was carried out using an ECX400 spectrometer (manufactured by JEOL) in the stated solvent at around room temperature unless otherwise stated. In all cases, NMR data were consistent with the proposed structures. Characteristic chemical shifts (δ) are given in parts-per-million using conventional abbreviations for designation of major peaks: e.g. s, singlet; d, doublet; t, triplet; q, quartet; dd, doublet of doublets; br, broad. Mass spectra were recorded using a MM-ES+APCI or ES mass spectrometer (G-1956A or G-6120B, manufactured by Agilent).

Compound preparation

Unless otherwise stated, organic solutions were dried over MgS0₄ Where the preparation of starting materials is not described, these are commercially available, known in the literature, or readily obtainable by those skilled in the art using standard procedures. Where it is stated that compounds were prepared analogously to earlier examples or intermediates or examples, it will be appreciated by the skilled person that the reaction time, number of equivalents of reagents and temperature can be modified for each specific reaction and that it may be necessary or desirable to employ different work-up or purification techniques. Where reactions are carried out using microwave irradiation, the microwave used is an Initiator 60 supplied by Biotage. The actual power supplied varies during the course of the reaction in order to maintain a constant temperature. Abbreviations

Ac = Acetyl

AcOH = Acetic acid (A-Phos)₂PdCI₂ = Bis(di-teri-butyl(4-dimethylaminophenyl)phosphine)- dichloropalladium(ll)

Boc = terf-Butoxycarbonyl

fBu = ferf-Butyl

CyPF-'Bu = (Dicyclohexylphosphino)ferrocenyl]ethyldi-te f-butylphosphine

DCM = Dichloromethane

DIPEA = Λ/,/V-Diisopropylethylamine

DMAP = A/,W-Dimethyl-4-aminopyridine

DMF = Λ/,/V-Dimethylformamide

DME = 1 ,2-Dimethoxyethane

Et = Ethyl

Et₃N = Triethylamine

EtOAc = Ethyl Acetate

EtOH = Ethanol

h = hours

HPLC = High performance liquid chromatography

LCMS = Mass spectrometry directed high pressure liquid chromatography mCPBA = m-Chloroperoxybenzoic acid

Me = Methyl

MeCN = Acetonitrile

MeOH = Methanol

min = minutes

NBS = /V-Bromosuccinimide

NMP = W-Methylpyrrolidinone

Pd₂(dba)₃ =Tris(dibenzylideneacetone)dipalladium(0)

Pd(dppf)CI₂ = 1 ,1 '-Bis(diphenylphosphino)ferrocenedichloropalladium(ll)

Pd(OAc)₂ = Palladium(ll) acetate

Pd(PPh₃) = Tetrakis(triphenylphosphine)palladium(0)

pTsOH = p-Toluenesulphonic acid

RT = Room temperature

SCX = Strong cation exchange

THF = Tetrahydrofuran TFA = Trifluoroacetic acid

UV = Ultraviolet

Xantphos = 4,5-Bis(diphenylphosphino)-9,9-dimethylxanthene

Intermediate 1

ferf-Butyl {frans-4-[(3-bromoimidazo[1 ,2-b]pyridazin-6- yl)amino]cyclohexyl}carbamate

A solution of 3-bromo-6-chloroimidazo[1 ,2-b]pyridazine (1.40 g, 6.02 mmol) in NMP (8 mL) was treated with frans-cyclohexane-1 ,4-diamine (2.05 g, 18.0 mmol, 3.0 eq) and stirred with microwave heating at 180°C for 30 min. It was then diluted with EtOAc (100 mL) and washed with water (2 x 100 mL). The organic layer was dried and concentrated in vacuo. Column chromatography (2M NH₃ in MeOH/EtOAc gradient) gave a pale yellow solid (981 mg, 52%); ¹H NMR (400 MHz, DMSO-cf₆) δ ppm 7.66 (d, J=10.1 Hz, 1 H), 7.45 (s, 1H), 6.95 (d, br, J=7.3 Hz, 1 H), 6.65 (d, J=9.6 Hz, 1 H), 3.63-3.53 (m, 1 H), 2.60-2.52 (m, 1 H), 2.08- 2.04 (m, 2H), 1.82-1.78 (m, 2H), 1.28-1.09 (m, 4H); m/z (ES+APCI)⁺: 310/312 [M+Hf. b) ferf-Butyl {frans-4-[(3-bromoimidazo[1,2-fe]pyridazin-6- yl)amino]cyclohexyl}carbamate

A solution of frans-/V-(3-bromo-imidazo[1 ,2-6]pyridazin-6-yl)-cyclohexane- ,4-diamine (1.80 g, 5.79 mmol) in THF (20 mL) was treated with Et₃N (1.21 mL, 8.70 mmol, 1.5 eq), di- fert-butyl dicarbonate (1.90 g, 8.70 mmol, 1.5 eq) and DMAP (71 mg, 0.58 mmol, 0.1 eq) and stirred at reflux for 18 h. Concentration in vacuo and column chromatography (20% MeOH/EtOAc) gave a pale yellow solid (1.60 g, 67%); ¹H NMR (400 MHz, DMSO-d₆) δ ppm 7.67 (d, J=9.6 Hz, 1 H), 7.46 (s, 1 H), 6.99 (d, br, J=7.3 Hz, 1 H), 6.76 (d, br, J=8.2 Hz, 1 H), 6.65 (d, J=9.6 Hz, 1 H), 3.59-3.52 (m, 1H), 3.28-3.22 (m, 1 H), 2.11-2.08 (m, 2H), 1.84- 1.81 (m, 2H), 1.38 (s, 9H), 1.30-1.23 (m, 4H); m/z (ES+APCI)⁺: 410/412 [M+H]⁺.

Intermediate 2

fert-Butyl tirans-4-({3-[2-(methylsulfonyl)pyrimidin-5-yl]imidazo[1 ,2-b]pyridazin-6- yl}amino)cyclohexyl]carbamate

a) fert-Butyl [frans-4-({3-[2-(methylsulfanyl)pyrimidin-5-yl]imidazo[1 ,2-b]pyridazin-6- yl}amino)cyclohexyl] carbamate

A mixture of ferf-butyl {£rans-4-[(3-bromoimidazo[1 ,2-ib]pyridazin-6- yl)amino]cyclohexyl}carbamate (2.0 g, 4.87 mmol, 1.0 eq), Pd(dppf)CI₂ (398 mg, 0.49 mmol), 2-(thiomethyl)pyrimidine-5-boronic acid (1.84 g, 7.31 mmol, 1.5 eq) and Cs₂C0₃ (6.35 g, 19.5 mmol, 4.0 eq) in dioxane (20 mL) and water (10 mL) was heated at 90°C for 2.5 h. Concentration in vacuo directly onto silica and column chromatography (0-10% MeOH/EtOAc) gave a pale yellow solid (2.0 g, 90%); ¹H NMR (400 MHz, DMSO-d_B) δ ppm 9.38 (s, 2H), 8.03 (s, 1 H), 7.77 (d, J=9.6 Hz, 1 H), 7.09 (d, br, J=6.9 Hz, 1 H), 6.83 (d, br, J=8.2 Hz, 1 H), 6.71 (d, J=9.6 Hz, 1 H), 3.53-3.47 (m, 1H), 3.31-3.26 (m, 1 H), 2.58 (s, 3H), 2.15-2.11 (m, 2H), 1.87-1.82 (m, 2H), 1.39 (s, 9H), 1.35-1.23 (m, 4H); m/z (ES+APCIf: 456 [M+H]⁺.

b) fert-Butyl [frans-4-({3-[2-(methylsulfonyl)pyrimidin-5-yl]imidazo[1 ,2-fa]pyridazin-6- yl}amino)cyclohexyl] carbamate

ferf-Butyl [irans-4-({3-[2-(methylsulfanyl)pyrimidin-5-yl]imidazo[1 ,2-/j]pyridazin yl}amino)cyclohexyl]carbamate (2.00 g, 4.39 mmol, 1.0 eq) in CH₂CI₂ (60 mL) was treated with mCPBA (2.38 g, 9.66 mmol, 2.2 eq) and stirred at RT for 2 h. The mixture was diluted with saturated aqueous Na₂S0₃ (20 mL) and CH₂CI₂ (50 mL) and washed with saturated aqueous NaHC0₃ (80 mL). The aqueous layer was extracted with CH₂CI₂ (50 mL), then the combined organic layers were washed with brine (60 mL), dried and concentrated to give an orange solid (2.1 g, 98%); H NMR (400 MHz, DMSO-cfe) δ ppm 9.80 (s, 2H), 8.30 (s, 1 H), 7.85 (d, J=9.6 Hz, 1 H), 7.24 (d, br, J=6.9 Hz, 1 H), 6.85 (d, br, J=8.2 Hz, 1 H), 6.82 (d, J=10.3 Hz, 1 H), 3.60-3.52 (m, 1 H), 3.44 (s, 3H), 3.33-3.25 (m, 1 H), 2.17-2.13 (m, 2H), 1.88-1.83 (m, 2H), 1.39 (s, 9H), 1.37-1.23 (m, 4H).

Example 1

trans-N-[Z-{2-{[(i -Methyl-1 H-pyrazol-3-yl)methyl]amino}pyrimidin-5-yl)imidazo[1 ,2- £>]pyridazin-6-yl]cyclohexane-1,4-diamine

A solution of intermediate 2 (60 mg, 0.12 mmol, 1.0 eq) in dioxane (2 mL) was treated with 1-(1 -methyl-1 H-pyrazol-3-yl)methanamine (54 mg, 0.49 mmol, 4.0 eq) and stirred at reflux for 4 h. Concentration in vacuo, purification by preparative HPLC and treatment with 4M HCI in dioxane (1 mL) followed by elution through an aminopropyl cartridge gave an off- white solid (6 mg, 11 %); ¹H NMR (400 MHz, DMSO-d_B) δ ppm 9.00 (br. s, 2H), 7.81-7.65 (m, 3H), 7.55 (d, J=2.3 Hz, 1 H), 6.93 (d, J=6.9 Hz, 1 H), 6.62 (d, J=9.6 Hz, 1 H), 6.13 (d, J=2.3 Hz, 1 H), 4.47 (d, J=6.0 Hz, 2H), 3.77 (s, 3H), 3.55-3.40 (m, 1 H), 2.64-2.54 (m, 1 H), 2.15-2.03 (m, 2H), 1.89-1.74 (m, 2H), 1.37-1.08 (m, 4H); m/z (ES+APCI)⁺: 419 [ +H]⁺.

Example 2

irans-/V-(3-{2-[(Pyridin-3-ylmethyl)am

yl)cyclohexane-1 ,4-diami

Following the method for example 1 using 1-(pyridin-3-yl)methanamine gave an off-white solid (12 mg, 9%); ¹H NMR (400 MHz, DMSO-cfe) δ ppm 9.02 (br. s, 2H), 8.58 (d, J=1.8 Hz, 1 H), 8.48-8.38 (m, 1 H), 8.08 (t, J=6.4 Hz, 1 H), 7.78-7.68 (m, 3H), 7.43-7.27 (m, 1 H), 6.94 (d, J=6.9 Hz, 1 H), 6.62 (d, J=9.6 Hz, 1 H), 4.55 (d, J=6.4 Hz, 2H), 3.53-3.41 (m, 1H), 2.64- 2.55 (m, 1H), 2.13-2.01 (m, 2H), 1.88-1.75 (m, 2H), 1.33-1.08 (m, 4H); m/z (ES+APCI)⁺: 416 [M+H]⁺. Example 3

irans-A/-[3-(2-{[(1- ethyl-1H-pyrazol-4-yl)methyl]amino}pyrimidin-5-yl)imidazo[1,2- Jb]pyridazin-6-yI]cycloh

Following the method for example 1 using 1-(1-methyl-1 H-pyrazol-4-yl)methanamine gave an off-white solid (4 mg, 7%); ¹H NMR (400 MHz, DMSO-cf₆) δ ppm 9.01 (s, 2H), 7.79-7.66 (m, 3H), 7.58 (s, 1 H), 7.41-7.33 (m, 1 H), 6.98-6.88 (m, 1 H), 6.65-6.58 (m, 1 H), 4.35 (d, J=6.0 Hz, 2H), 3.83-3.72 (m, 3H), 3.56-3.42 (m, 1H), 2.64-2.55 (m, 1H), 2.17-2.02 (m, 2H), 1.90-1.73 (m, 2H), 1.35-1.06 (m, 4H); m/z (ES+APCIf: 419 [M+H]⁺. Example 4

irans-W-(3-{2-[(Pyridin-2-ylmethyl)amino]pyrimidin-5-yl}imidazo[1_J^

yl)cyclohexane-1,4-diami

Following the method for example 1 using 1-(pyridin-2-yl)methanamine gave an off-white solid (15 mg, 27%); ¹H NMR (400 MHz, DMSO-d₆) δ ppm 9.00 (br. s, 2H), 8.50 (dt, .7=0.9, 2.5 Hz, 1 H), 8.04-7.96 (m, 1 H), 7.78-7.67 (m, 3H), 7.32 (d, J=7.8 Hz, 1 H), 7.24 (ddd, J=0.9, 4.8, 7.6 Hz, 1 H), 6.93 (d, J=6.9 Hz, 1H), 6.62 (d, J=9.6 Hz, 1 H), 4.64 (d, J=6.4 Hz, 2H), 3.55-3.40 (m, 1 H), 2.66-2.56 (m, 1 H), 2.18-2.02 (m, 2H), 1.89-1.76 (m, 2H), 1.31-1.06 (m, 4H); m/z (ES+APCI)⁺: 4 6 [M+H]⁺.

Intermediate 3

ferf-Butyl (irans-4-{[3-(2-aminopyrimidin-5-yI)imidazo[1,2-b]pyrid

yI]amino}cycIohexyl)carbamate

A mixture of intermediate 1 (1.20 g, 2.92 mmol, 1.0 eq), 2-aminopyrimidine-5-boronic acid pinacol ester (970 mg, 4.39 mmol, 1.5 eq), Cs₂C0₃ (3.81 g, 11.7 mmol, 4.0 eq), water (6 ml_) and dioxane (12 ml_) was degassed with N₂, then Pd(dppf)CI₂ (238 mg, 0.29 mmol, 0.1 eq) was added and the mixture heated at 90°C for 5 h. The mixture was allowed to cool, then concentrated to dryness and purified by chromatography on silica gel (2-20% MeOH/EtOAc) to give a beige solid (1.07 g, 86%); ¹H NMR (400 MHz, DMSO-d₆) δ ppm 8.96 (s, 2H), 7.78 (s, 1 H), 7.70 (d, J=9.6 Hz, 1H), 6.96 (d, J=6.9 Hz, 1 H), 6.87-6.78 (m, 3H), 6.62 (d, J=9.6 Hz, 1 H), 3.52-3.42 (m, 1 H), 3.30-3.21 (m, 1 H), 2.17-2.08 (m, 2H), 1.90-1.79 (m, 2H), 1.38 (s, 9H), 1.32-1.21 (m, 4H); m/z (ES+APCI)⁺: 425 [M+Hf.

Example 5

irans-/V-{3-[2-(Pyridin-3-ylamino)pyrimidin-5-yl]imidazo[1 ,2- ]pyridazi

yI}cycIohexane-1,4-diami

Intermediate 3 (90 mg, 0.21 mmol, 1.1 eq), 3-bromopyridine (19 pL, 30 mg, 0.19 mmol, 1 .0 eq) and NaO'Bu (73 mg, 0.76 mmol, 4.0 eq) were added to a pre-stirred solution of Pd(OAc)₂ (4.3 mg, 0.1 eq) and CyPF-'Bu (10.5 mg, 0.1 eq) in dioxane (1.5 mi_) and the mixture was heated at 80°C for 40 h. The mixture was allowed to cool, then 4M HCI/dioxane (1 ml_) was added and the mixture stirred for 2 h. The mixture was concentrated to dryness and purified by prep-HPLC (pH 10) to give an orange/brown solid (24 mg, 28%); Ή NMR (400 MHz, DMSO-d_B) δ ppm 10.14-10.08 (m, 1 H), 9.29 (s, 2H), 8.94 (d, J=1.8 Hz, 1 H), 8.28-8.24 (m, 1 H), 8.19-8.16 (m, 1 H), 7.93 (s, 1 H), 7.75 (d, J=9.6 Hz, 1 H), 7.36-7.32 (m, 1 H), 7.03 (d, J=6.9 Hz, 1 H), 6.67 (d, J=9.6 Hz, 1 H), 3.57-3.47 (m, 1 H), 2.66-2.58 (m, 1 H), 2.16-2.08 (m, 2H), 1.88-1.80 (m, 2H), 1.32-1.1 1 (m, 4H); m/z (ES+APCI)⁺: 402 [M+Hf. Example 6

f rans-N-{3-[2-(Py r i d i n -2-y I am i n o) py r i m id i n -5-y I] i m id azo [1 , 2-b] py rid azi n -6- yl}cyclohexane-1,4-diamine

Intermediate 3 (90 mg, 0.21 mmol, 1.1 eq), 2-chloropyridine (18 μΙ_, 22 mg, 0.19 mmol, 1.0 eq) and NaO'Bu (73 mg, 0.76 mmol, 4.0 eq) were added to a pre-stirred solution of Pd(OAc)₂ (4.3 mg, 0.1 eq) and CyPF-'Bu (10.5 mg, 10 moi%) in DME (1.5 mL) and the mixture was heated at 80°C for 3 h. The mixture was allowed to cool, diluted with CH₂CI₂ and passed through an Isolute silica cartridge (1 g) eluting with DCM/MeOH (7:3). The eluent was concentrated under reduced pressure then stirred in MeOH (3 mL) and 4M HCI/dioxane (2 mL) for 40 min. The mixture was concentrated and purified by prep-HPLC (pH 10) to give a white solid (5 mg, 6%); ¹H NMR (400 MHz, CD₃OD) δ ppm 9.24 (s, 2H), 8.39-8.34 (m, 1 H), 8.29-8.24 (m, 1 H), 7.81 (s, 1 H), 7.80-7.76 (m, 1 H), 7.62 (d, .7=10.1 Hz, 1 H), 7.05-7.00 (m, 1H), 6.69 (d, J=9.6 Hz, 1 H), 3.73-3.63 (m, 1 H), 2.90-2.80 (m, 1 H), 2.31- 2.22 (m, 2H), 2.07-1.98 (m, 2H), 1.50-1.30 (m, 4H); m/z (ES+APCI)⁺: 402 [M+H]⁺.

Example 7

irans-W-{3-{2-[(5-Fluoropyridin-2-yl)amino]pyrimidin-5-yl}imidazo[1 ,2-b]pyridazin-6- yl)cyclohexane-1,4-diamine

Intermediate 3 (50 mg, 0.12 mmol, 1.0 eq), 2-chloro-5-(trifluoromethyl)pyridine (21 mg, 0.12 mmol, 1.0 eq), Pd(OAc)₂ (2.7 mg, 0.1 eq), Xantphos (6.9 mg, 0.1 eq) and Cs₂C0₃ (156 mg, 0.48 mmol, 4.0 eq) in dioxane (0.8 mL) under N₂ were heated at 100°C for 4 h. The mixture was allowed to cool, then 4M HCI/dioxane (1 mL) was added and the mixture stirred for 2 h. The mixture was concentrated to dryness then purified by prep-HPLC (pH 10) to give a white solid (3 mg, 5%); H NMR (400 MHz, DMSO-cQ δ ppm 10.72 (br. s, 1H), 9.37 (s, 2H), 8.67-8.64 (m, 1 H), 8.51-8.47 (m, 1 H), 8.15 (dd, J=8.9, 2.5 Hz, 1 H), 7.99 (s, 1 H), 7.77 (d, J=9.6 Hz, 1 H), 7.08 (d, J=6.4 Hz, 1 H), 6.70 (d, J=9.6 Hz, 1 H), 3.57-3.49 (m, 1 H), 2.79-2.70 (m, 1 H), 2.19-2.10 (m, 2H), 1.92-1.84 (m, 2H), 1.33-1.21 (m, 4H); m/z (ES+APCI)⁺: 470 [M+H]⁺.

Example 8

frans-W-{3-t2-(Pyrimidin-2-ylamino)pyrimidin-5-yl]imidazo[1,2--3]pyridazin-6- yl}cyclohexane-1,4-diami

Intermediate 3 (80 mg, 0.19 mmol, 1.0 eq), 2-chloropyrimidine (22 mg, 0.19 mmol, 1.0 eq), Pd(OAc)₂ (4.3 mg, 0.1 eq), Xantphos (11 mg, 0.1 eq) and Cs_zC0₃ (248 mg, 0.76 mmol, 4.0 eq) in dioxane (1 mL) under N₂ were heated at 90°C for 10 h. The mixture was allowed to cool, then 4M HCI/dioxane (1 mL) was added and the mixture stirred for 2 h. The mixture was concentrated to dryness then purified by prep-HPLC (pH 1) and eluted through an Isolute aminopropyl cartridge (0.5 g) to give a white solid (8 mg, 10%); ¹H NMR (400 MHz, DMSO-de) δ ppm 10.45 (br. s, 1H), 9.30 (s, 2H), 8.60 (d, J-5.0 Hz, 2H), 7.97 (s, 1H), 7.78 (d, J=9.6 Hz, 1 H), 7.08-7.03 (m, 2H), 6.70 (d, J=9.6 Hz, 1 H), 3.60-3.50 (m, 1 H), 2.82-2.73 (m, 1H), 2.18-2.09 (m, 2H), 1.92-1.84 (m, 2H), 1.34-1.20 (m, 4H); m/z (ES+APCI)⁺: 403 [M+H]⁺.

Example 9

frans-W-{3-[2-(Pyrazin-2-ylamino)pyrimidin-5-yl]imidazo[1,2-b]pyridazin-6- yl}cyclohexane-1 ,4-diamine

Following the method for example 8 using 2-chloropyrazine gave a pale yellow solid (8 mg, 10%); ¹H NMR (400 MHz, DMSO-cfc) δ ppm 10.52 (br. s, 1 H), 9.52 (d, J=1.4 Hz, 1 H), 9.34 (s, 2H), 8.36-8.34 (m, 1 H), 8.24 (d, J=2.3 Hz, 1H), 7.97 (s, 1 H), 7.77 (d, J=9.6 Hz, 1 H), 7.04 (d, J=6.9 Hz, 1 H), 6.70 (d, J=9.6 Hz, 1H), 3.58-3.49 (m, 1 H), 2.76-2.65 (m, 1 H), 2.17- 2.09 (m, 2H), 1.90-1.82 (m, 2H), 1.34-1.16 (m, 4H); m/z (ES+APCIf: 403 [M+H]⁺.

Example 10

frans-A/-[3-(2^[4-(Trifluoromethyl)pyridin-2-yl]amino}pyrimidin-5-yl)imidazo[1,2- £)]pyridazin-6-yl]cycIoh

Following the method for example 8 using 2-chloro-4-(trifluoromethyl)pyridine gave an off- white solid (4 mg, 4%); ¹H NMR (400 MHz, DMSO-cfe) δ ppm 10.70 (br. s, 1 H), 9.43 (s, 2H), 8.73 (s, 1 H), 8.56 (d, J=5.0 Hz, 1 H), 8.02 (s, 1 H), 7.78 (d, J=10.1 Hz, 1 H), 7.35-7.31 (m, 1 H), 7.06 (d, J=6.9 Hz, 1 H), 6.70 (d, J=9.6 Hz, 1 H), 3.59-3.49 (m, 1 H), 2.66-2.57 (m, 1 H), 2.17-2.09 (m, 2H), 1.89-1.80 (m, 2H), 1.34-1.11 (m, 4H); m/z (ES+APCI)⁺: 470 [M+H]⁺.

Example 11

frans-W-(3-{2-[(5-Chloropyrimidin-2-yl)amino]py

6-yl)cyclohexane-1 ,4-diamine

Following the method for example 8 using 2,5-dichloropyrimidine gave a pale yellow solid (20 mg, 24%); H NMR (400 MHz, DMSO-d₆) δ ppm 9.33 (s, 2H), 8.69 (s, 2H), 7.97 (s, 1H), 7.77 (d, J=10.1 Hz, 1 H), 7.03 (d, J=6.9 Hz, 1 H), 6.70 (d, J=10.1 Hz, 1H), 3.59-3.48 (m, 1 H), 2.69-2.57 (m, 1 H), 2.14-2.05 (m, 2H), 1.87-1.77 (m, 2H), 1.32-1.10 (m, 4H); m/z (ES+APCI)⁺: 437/439 [M+Hf.

Intermediate 4

fert-Butyl 4- [3-(2-aminopyrimidin-5-yl)imidazo[1,2-6]pyridazin-6-yl]amino}piperidine- 1-carboxylate

a) ierf-Butyl 4-[(3-bromoimidazo[1 ,2-b]pyridazin-6-yl)amino]piperidine-1 -carboxylate

A solution of 3-bromo-6-chloroimidazo[1 ,2-b]pyridazine (3.00 g, 12.9 mmol 1.0 eq) in NMP (15 ml_) was treated with te/f-butyl 4-aminopiperidine-1 -carboxylate (5.10 g, 25.8 mmol, 2.0 eq), DIPEA (5.60 mL, 32.3 mmol, 2.5 eq) and heated at 130°C for 5 h. The reaction mixture was diluted with DCM (100 mL) and washed with de-ionised water (3 x 150 mL). The separated organic was concentrated in vacuo and column chromatography (10-80% EtOAc/pet ether) gave a brown solid (3.01 g, 59%); ¹H NMR (400 MHz, DMSO-d₆) δ ppm 7.71 (d, J=9.6 Hz, 1 H), 7.48 (s, 1 H), 7.10 (d, br, J=7.3 Hz, 1H), 6.68 (d, J=10.1 Hz, 1H), 3.87-3.82 (m, 3H), 3.02-2.93 (m, 2H), 2.02-1.98 (m, 2H), 1.41 (s, 9H), 1.40-1.31 (m, 2H); m/z (ES+APCI)⁺: 396/398 [M+H]⁺.

b) fert-Butyl 4-{t3-(2-aminopyrimidin-5-yl)imidazo[1,2 ]pyridazin-6- yl]amino}piperidine-1 -carboxylate

Following the procedure for intermediate 3 using terf-butyl 4-[(3-bromoimidazo[1 ,2- i ]pyridazin-6-yl)amino]piperidine-1-carboxylate gave a beige solid (324 mg, 100%); ¹H NMR (400 MHz, DMSO-d₆) δ ppm 8.95 (s, 2H), 7.79 (s, 1 H), 7.74 (d, J=9.6 Hz, 1 H), 7.06 (d, .7=6.4 Hz, 1 H), 6.85 (s, 2H), 6.65 (d, J=9.6 Hz, 1 H), 3.93-3.83 (m, 2H), 3.80-3.71 (m, 1 H), 3.01-2.88 (m, 2H), 2.06-2.00 (m, 2H), 1.42 (s, 9H), 1.39-1.31 (m, 2H); m/z (ES+APCIf: 411 [M+H]⁺.

Example 12

W-(Piperidin-4-yI)-3-[2-(pyridin-2-yIamino)pyri^

amine

Intermediate 4 (80 mg, 0.19 mmol, 1.0 eq), 2-chloropyridine (20 μΙ_, 24 mg, 0.21 mmol, 1.1 eq), Pd(OAc)₂ (4.3 mg, 0.1 eq), Xantphos (11 mg, 0.1 eq) and Cs₂C0₃ (248 mg, 0.76 mmol, 4.0 eq) in dioxane (1.5 mL) under N₂ were heated at 90°C for 22 h. The mixture was allowed to cool, then 4M HCI/dioxane (1 mL) was added and the mixture stirred for 4 h. The mixture was concentrated to dryness then purified by prep-HPLC (pH 1) and eluted through an Isolute aminopropyl cartridge (0.5 g) to give a white solid (10 mg, 14%); ¹H NMR (400 MHz, DMSO-cfe) δ ppm 10.01 (s, 1 H), 9.27 (s, 2H), 8.32-8.24 (m, 2H), 7.94 (s, 1 H), 7.81-7.72 (m, 2H), 7.10 (d, J=6.9 Hz, 1 H), 7.03-6.97 (m, 1 H), 6.71 (d, J=9.6 Hz, 1 H), 3.77-3.66 (m, 1H), 3.08-2.99 (m, 2H), 2.70-2.60 (m, 2H), 2.07-1.98 (m, 2H), 1.46-1.33 (m, 2H); m/z (ES)⁺: 388 [M+H]⁺. Example 13

irans- V-(3-{2-[(3-Methy I pyri d i n -2-y I)am

yl)cycIohexane-1 ,4-diami

Intermediate 3 (80 mg, 0.19 mmol, 1.0 eq), 2-chloro-3-methylpyridine (23 μί, 27 mg, 0.21 mmol, 1.1 eq), Pd(OAc)₂ (4.3 mg, 0.1 eq), Xantphos (11 mg, 0.1 eq) and Cs₂C0₃ (248 mg, 0.76 mmol, 4.0 eq) in dioxane (1.5 mL) under N₂ were heated at 90°C for 22 h. The mixture was allowed to cool, then 4M HCI/dioxane (1 mL) was added and the mixture stirred for 2 h. The mixture was concentrated to dryness then purified by prep-HPLC (pH 10) give a yellow solid (2 mg, 3%); ¹H NMR (400 MHz, DMSO-d₆) δ ppm 9.57 (s, 1 H), 9.12 (s, 2H), 8.25-8.21 (m, 1 H), 7.84 (s, 1 H), 7.73 (d, J=9.6 Hz, 1H), 7.68-7.63 (m, 1 H), 7.14 (dd, J=7.3, 5.0 Hz, 1 H), 6.97 (d, J=6.9 Hz, 1 H), 6.65 (d, J= 0.1 Hz, 1 H), 3.55-3.46 (m, 1 H), 2.65-2.57 (m, 1 H), 2.22 (s, 3H), 2.13-2.05 (m, 2H), 1.85-1.77 (m, 2H), 1.29-1.11 (m, 4H); m/z (ES+APCI)⁺: 416 [M+H]⁺.

Example 14

frans-W-(3-{2-[(3-Fluoropyridin-2-yl)amino]pyrimidin-5-yl}imidazo[1,2- 3]pyridazin-6- yl)cyclohexane-1 ,4-diami

Following the procedure for example 12 using intermediate 3 and 2-chloro-3-fluoropyridine gave a yellow solid (12 mg, 15%); Ή NMR (400 MHz, DMSO-cf₆) δ ppm 10.04 (br. s, 1 H), 9.16 (s, 2H), 8.25-8.19 (m, 1 H), 7.87 (s, 1H), 7.77-7.69 (m, 2H), 7.32-7.23 (m, 1 H), 6.99 (d, J=6.9 Hz, 1 H), 6.67 (d, J=10.5 Hz, 1 H), 3.57-3.44 (m, 1H), 2.65-2.56 (m, 1 H), 2.14-2.03 (m, 2H), 1.86-1.76 (m, 2H), 1.31-1.08 (m, 4H); m/z (ES+APCI)⁺: 420 [M+H]⁺. Example 15

frans-A/-(3-{2-[(6-Methylpyridin-2-yl)amino]pyrimidin-S-yl}imidazo[1,2-^]pyridazin-6- yl)cyclohexane-1,4-diami

Following the method for example 13 using 2-chloro-6-methylpyridine gave a white solid

(17 mg, 22%); H NMR (400 MHz, DMSO-cf_B) δ ppm 9.86 (s, 1 H), 9.26 (s, 2H), 8.10 (d, J=8.2 Hz, 1 H), 7.92 (s, 1 H), 7.76 (d, J=9.6 Hz, 1 H), 7.66 (t, J=7.8 Hz, 1H), 7.00 (d, =6.9 Hz, 1 H), 6.87 (d, J=7.3 Hz, 1 H), 6.68 (d, J=9.6 Hz, 1 H), 3.58-3.46 (m, 1 H), 2.65-2.56 (m, 1 H), 2.40 (s, 3H), 2.15-2.06 (m, 2H), 1.87-1.78 (m, 2H), 1.33-1.10 (m, 4H); m/z (ES+APCI)⁺: 416 [M+H]⁺.

Example 16

frans-W-(3-{2-[(5-Chloropyridin-2-yI)amino]pyri

yl)cyclohexane-1 ,4-diamine

Intermediate 3 (80 mg, 0.19 mmol, 1.0 eq), 2,5-dichloropyridine (31 mg, 0.21 mmol, 1.1 eq), Pd(OAc)₂ (4.3 mg, 0.1 eq), Xantphos (11 mg, 0.1 eq) and Cs₂C0₃ (248 mg, 0.76 mmol, 4.0 eq) in dioxane (1.5 mL) under N₂ were heated at 90°C for 18 h. The mixture was allowed to cool, then 4M HCI/dioxane (1 mL) was added and the mixture stirred for 3 h. The mixture was concentrated to dryness then purified by prep-HPLC (pH 1) and eluted through an Isolute aminopropyl cartridge (0.5 g) to give a white solid (2 mg, 2%); ¹H NMR (400 MHz, DMSO-c/₆) δ ppm 10.37 (s, 1 H), 9.31 (s, 2H), 8.35-8.30 (m, 2H), 7.95-7.93 (m, 1 H), 7.91- 7.86 (m, 1 H), 7.75 (d, J=9.6 Hz, 1 H), 7.03 (d, J=6.9 Hz, 1 H), 6.69 (d, J=9.6 Hz, 1H), 3.57- 3.47 (m, 1 H), 2.57-2.52 (m, 1 H), 2.14-2.05 (m, 2H), 1.87-1.78 (m, 2H), 1.32-1.12 (m, 4H); m/z (ES+APCI)⁺: 436/438 [M+H]⁺. Example 17

irans-W-(3-{2-[(5-Fluoropyridin-2-yl)amino]pyrimidin-5-yl}imidazo[1,2-fa]pyridazin-6- yl)cyclohexane-1,4-diamine

Following the method for example 16 using 2-chloro-5-fluoropyridine gave an off-white solid (3 mg, 4%); ¹H NMR (400 MHz, DMSO-cf₆) δ ppm 10.23 (s, 1 H), 9.28 (s, 2H), 8.32- 8.25 (m, 2H), 7.94-7.91 (m, 1 H), 7.77-7.70 (m, 2H), 7.02 (d, J=6.9 Hz, 1 H), 6.68 (d, J=9.6 Hz, 1 H), 3.58-3.46 (m, 1H), 2.65-2.56 (m, 1 H), 2.15-2.06 (m, 2H), 1.87-1.78 (m, 2H), 1.32- 1.10 (m, 4H); m/z (ES+APCI)⁺: 420 [M+H]⁺. Example 18

irans-W-(3-{2-[(5-Methylpyridin-2-yl)amino]pyrimidin-5-yl}imidazo[1 ,2-6]pyridazin-6- yl)cyclohexane-1,4-diamine

Following the method for example 16 using 2-chloro-5-methylpyridine gave an off-white solid (4 mg, 5%); ¹H NMR (400 MHz, DMSO-d_B) δ ppm 9.92 (s, 1 H), 9.26 (s, 2H), 8.17 (d, J=8.7 Hz, 1 H), 8.14-8.11 (m, 1 H), 7.92 (s, 1 H), 7.75 (d, J=9.6 Hz, 1 H), 7.60 (dd, J=2.3, 8.7 Hz, 1 H), 7.00 (d, J=6.9 Hz, 1 H), 6.67 (d, J=9.6 Hz, 1 H), 3.57-3.47 (m, 1 H), 2.65-2.56 (m, 1 H), 2.25 (s, 3H), 2.14-2.07 (m, 2H), 1.86-1.79 (m, 2H), 1.32-1.13 (m, 4H); m/z (ES+APCI)⁺: 416 [M+H]⁺.

Example 19

-rans-W^3-{2-[(6-Methylpyridazin-3-yl)amino]pyrimidin-5-yl}imidazo[1,2-b]pyri

6-yl)cyclohexane-1,4-diamine

Following the method for example 16 using 3-chloro-6-methylpyridazine gave a yellow solid (5 mg, 6%); ¹H NMR (400 MHz, DMSO-d₆) δ ppm 10.61 (br. s, 1 H), 9.29 (s, 2H), 8.39 (d, J=9.2 Hz, 1H), 7.94 (s, 1 H), 7.76 (d, J=9.6 Hz, 1 H), 7.54 (d, J=9.2 Hz, 1 H), 7.03 (d, J=6.9 Hz, 1 H), 6.69 (d, J=9.6 Hz, 1 H), 3.58-3.46 (m, 1 H), 2.66-2.59 (m, 1 H), 2.57 (s, 3H), 2.16-2.05 (m, 2H), 1.88-1.79 (m, 2H), 1.34-1.12 (m, 4H); m/z (ES+APCI)⁺: 417 [M+H]⁺.

Example 20

irans-W-{3-[2-{Quinolin-2-ylamino)pyrimidin-5-yl]imidazo[1,2-d]pyridazin-6- yl}cyclohexane-1 ,4-diamine

Following the method for example 16 using 2-chloroquinoline gave a yellow solid (42 mg, 49%); ¹H NMR (400 MHz, DMSO-d₆) δ ppm 9.35 (s, 2H), 8.45 (d, J=9.2 Hz, 1H), 8.27 (d, J=8.7 Hz, 1 H), 8.15 (s, 1 H), 7.96 (d, J=7.8 Hz, 1H), 7.93-7.81 (m, 3H), 7.78 (t, J=7.6 Hz, 1 H), 7.53 (t, J=7.3 Hz, 1H), 7.37-7.31 (m, 1H), 6.88 (d, J=9.6 Hz, 1H), 3.64-3.51 (m, 1H), 3.16-3.06 (m, 1H), 2.27-2.17 (m, 2H), 2.08-2.00 (m, 2H), 1.55-1.28 (m, 4H); m/z (ES+APCI)⁺: 452 [M+Hf.

Example 21

frans-A/-{3-[2-(Quinoxalin-2-ylamino)pyrimidin-5-yl]imidazo[1,2-/3]pyrid

yl}cyclohexane-1,4-diamine

Following the method for example 16 using 2-chloroquinoxaline gave an orange solid (16 mg, 19%); ¹H NMR (400 MHz, DMSO-cfe) δ ppm 9.71 (s, 1H), 9.36 (s, 2H), 8.04-7.97 (m, 2H), 7.87-7.83 (m, 1H), 7.81-7.73 (m, 2H), 7.68-7.61 (m, 1H), 7.07 (d, J=6.9 Hz, 1H), 6.71 (d, J=10.1 Hz, 1H), 3.61-3.50 (m, 1H), 2.90-2.79 (m, 1 H), 2.21-2.11 (m, 2H), 1.97-1.87 (m, 2H), 1.38-1.23 (m, 4H); m/z (ES+APCI)⁺: 453 [M+H]⁺.

Example 22 W-(Piperidin-4-yI)-3-[2-(pyrazin-2-yIami^^

amine

To a solution of intermediate 4 (100 mg, 0.24 mmol, 1.0 eq), 2-chloropyrazine (28 mg, 0.30 mmol, 1.2 eq) and Cs₂C0₃ (316 mg, 0.97 mmol, 4.0 eq) in dioxane (3.0 mL) was added Pd(OAc)₂ (6 mg, 0.1 eq) and Xantphos (16 mg, 0.1 eq). The reaction mixture was heated in the microwave at 130°C for 50 min, diluted with DCM (20 mL) and washed with de-ionised water (20 mL). The organic was separated and treated with 4M HCl in dioxane (2 mL) and methanol (5 mL). The product was purified by preparative LCMS and passed through an aminopropyl cartridge to give an off-white solid (5 mg, 5%); ¹H NMR (400 MHz, DMSO-c ₆) δ ppm 10.50 (s, 1 H), 9.53 (d, J=1.8 Hz, 1 H), 9.35 (s, 2H), 8.35 (dd, J=1.6, 2.5 Hz, 1 H), 8.24 (d, J=2.3 Hz, 1 H), 7.98 (s, 1 H), 7.77 (d, J=9.6 Hz, 1H), 7.10 (d, J=7.3 Hz, 1 H), 6.71 (d, J=9.6 Hz, 1 H), 3.82-3.54 (m, 1 H), 3.08-2.90 (m, 2H), 2.64-2.55 (m, 2H), 2.10-1.92 (m, 2H), 1.49-1.29 (m, 2H); m/z (ES+APCI)⁺: 389 [M+H]⁺.

Example 23

3-{2-[(5-Chloropyrimidin-2-yl)amino]pyrimidin-5-^

b]pyridazin-6-amine

Following the method for example 22 using 2,5-dichloropyrimidine gave a white solid (9 mg, 9%); ¹H NMR (400 MHz, DMSO-de) δ ppm 10.73 (s, 1 H), 9.33 (s, 2H), 8.68 (s, 2H), 7.98 (s, 1 H), 7.77 (d, J=9.6 Hz, 1 H), 7.09 (d, J=6.9 Hz, 1 H), 6.72 (d, J=9.6 Hz, 1 H), 3.78-3.59 (m, 1 H), 3.07-2.88 (m, 2H), 2.61-2.54 (m, 2H), 2.07-1.90 (m, 2H), 1.38-1.29 (m, 2H); m/z (ES+APCI)⁺: 423/425 [M+H]⁺.

Example 24

W-(Piperidin-4-yl)-3-(2-{[6-(trifluoromethyI)pyridin-2-yl]amino}pyrimidin-5- yl)imidazo[1,2-b]pyridazin-6-amine

Following the method for example 22 using 2-chloro-6-(trifluoromethyl)pyridine gave a white solid (47 mg, 42%); ¹H NMR (400 MHz, DMSO-ci_s) δ ppm 10.55 (s, 1 H), 9.31 (s, 2H), 8.55 (d, J=8.2 Hz, 1H), 8.04 (t, J=7.8 Hz, 1 H), 7.96 (s, 1 H), 7.78 (d, J=10.1 Hz, 1 H), 7.47 (d, J=6.9 Hz, 1 H), 7.11 (d, J=6.9 Hz, H), 6.72 (d, J=10.1 Hz, 1 H), 3.76-3.66 (m, 1 H), 3.10- 2.95 (m, 2H), 2.74-2.57 (m, 2H), 2.13-1.91 (m, 2H), 1.46-1.33 (m, 2H); m/z (ES+APCI)⁺: 456 [M+H]⁺. Example 25

3-{2-[(5-Fluoropyridin-2-yl)amino]pyrimidin-5-yl}-yV-(piperidin-4-yl)imidazo[1 ,2- b]pyridazin-6-amine

Following the method for example 22 using 2-chloro-5-fluoropyridine gave a white solid (6 mg, 6%); ¹H NMR (400 MHz, DMSO-d₆) δ ppm 10.20 (s, 1H), 9.27 (s, 2H), 8.32-8.25 (m, 2H), 7.93 (s, 1 H), 7.81-7.70 (m, 2H), 7.07 (d, J=6.9 Hz, 1H), 6.70 (d, J=9.6 Hz, 1 H), 3.73- 3.59 (m, 1 H), 3.03-2.94 (m, 2H), 2.62-2.53 (m, 2H), 2.03-1.94 (m, 2H), 1.41-1.26 (m, 2H); m/z (ES+APCI)⁺: 406 [ +H]⁺.

Example 26

3-{2-[(3-Fluoropyridin-2-yl)amino]pyrimidin-5-yl}-W-(piperidin-4-yl)imidazo[1,2^ b]pyridazin-6-amine

Following the method for example 22 using 2-chloro-3-fluoropyridine gave a white solid (24 mg, 24%); ¹H NMR (400 MHz, DMSO-d₆) δ ppm δ ppm 9.99 (s, 1 H), 9.13 (s, 2H), 8.23 (td, J=4.6, 1.4 Hz, 1 H), 7.87 (s, 1 H), 7.77 (d, J=9.6 Hz, 1 H), 7.76-7.70 (m, 1 H), 7.29 (ddd, .7=8.4, 4.9, 3.7 Hz, 1 H), 7.10 (d, J=6.9 Hz, 1 H), 6.69 (d, J=9.6 Hz, 1H), 3.83-3.61 (m, 1 H), 3.13-3.03 (m, 2H), 2.78-2.63 (m, 2H), 2.14-1.94 (m, 2H), 1.59-1.31 (m, 2H); m/z (ES+APCIf: 406 [M+H]⁺. Example 27

3-{2-[(3-Fluoropyridin-2-yl)amino]pyrimidin-5-yl}-/V-(1-methylpiperidin-4- yl)imidazo[1,2-b]pyridazin-6-amine

To a solution of 3-{2-[(3-fluoropyridin-2-yl)amino]pyrimidin-5-yl}-W-(piperidin-4- yl)imidazo[1 ,2-j ]pyridazin-6-amine (30 mg, 0.07 mmol, 1.0 eq) in THF (0.5 mL) was added formaldehyde (37% aqueous, 6 pl_, 0.07 mmol, 1.0 eq), AcOH (8 μΙ_, 0.148 mmol, 2.0 eq) and sodium triacetoxyborohydride (31 mg, 0.015 mmol, 2.0 eq). The reaction mixture was stirred for 2 h at room temperature and concentrated in vacuo. Purification by preparative HPLC gave an off-white solid (12 mg, 39%); ¹H NMR (400 MHz, DMSO-cf₆) δ ppm 10.01 (d, J=4A Hz, 1 H), 9.15-9.12 (m, 2H), 8.24-8.21 (m, 1 H), 7.87 (s, 1 H), 7.77-7.69 (m, 2H), 7.29 (ddd, J=8.1 , 4.7, 3.7 Hz, 1 H), 7.09-7.03 (m, 1 H), 6.69 (d, J=9.6 Hz, 1 H), 3.64-3.50 (m, 1H), 2.82-2.70 (m, 2H), 2.18 (s, 3H), 2.09-1.90 (m, 4H), 1.54-1.31 (m, 2H); m/z (ES+APCI)⁺: 420 [M+H]⁺.

Example 28

W-(Piperidin-4-yl)-3-(2-{[4-(trifluoromethyl)pyridin-2-yl]amino}pyrimidin-5- yl)imidazo[1 ,2-b]pyridazin-6-amine

Following the method for example 22 using 2-chloro-4-(trifluoromethyl)pyridine gave a yellow solid (5 mg, 5%); ¹H NMR (400 MHz, DMSO-cf₆) δ ppm 10.66 (s, 1 H), 9.41 (s, 2H), 8.74 (d, .7=0.9 Hz, 1 H), 8.56 (d, J=5.0 Hz, 1 H), 8.01 (s, 1 H), 7.77 (d, =9.6 Hz, 1 H), 7.33 (dd, J=1.4, 5.5 Hz, 1 H), 7.10 (d, J=6.9 Hz, 1 H), 6.71 (d, J=9.6 Hz, 1 H), 3.81-3.54 (m, 1H), 3.12-2.90 (m, 2H), 2.64-2.53 (m, 2H), 2.11-1.95 (m, 2H), 1.43-1.22 (m, 2H); m/z (ES+APCI)⁺: 456 [M+H]⁺.

Example 29

3-{2-[(6- ethylpyridazin-3-yl)amino]pyrimidin-5-yl}-/V-(piperidin-4-yl)imidazo[1,2- J ]pyridazin-6-amine

Following the method for example 22 using 3-chloro-6-methylpyridazine gave an off-white solid (4 mg, 4%); ¹H NMR (400 MHz, DMSO-d₆) δ ppm 10.58 (s, 1H), 9.28 (s, 2H), 8.38 (d, J=9.2 Hz, 1 H), 7.94 (s, 1 H), 7.76 (d, J=9.6 Hz, 1 H), 7.54 (d, J=9.2 Hz, 1 H), 7.08 (d, J=6.9 Hz, 1 H), 6.71 (d, J=9.6 Hz, 1 H), 3.80-3.53 (m, 1 H), 3.10-2.88 (m, 2H), 2.62-2.53 (m, 5H), 2.10-1.88 (m, 2H), 1.43-1.24 (m, 2H); m/z (ES+APCI)⁺: 403 [M+H]⁺.

Example 30

irans-A/-[3-(2-{[5-(Trifluoromethyl)pyrazin-2-ynamino}pyrimidin-5-yl)imidazo[1,2- b]pyridazin-6-yl]cycloh

Following the method for example 16 using 5-chloro-2-trifluoromethylpyrazine gave a yellow solid (3 mg, 3%); ¹H NMR (400 MHz, DMSO-d_B) δ ppm 9.63 (s, 1 H), 9.43 (s, 2H), 8.83-8.81 (m, 1 H), 8.03 (s, 1 H), 7.77 (d, J=9.6 Hz, 1 H), 7.06 (d, J=6.9 Hz, 1 H), 6.72 (d, J=9.6 Hz, 1 H), 3.59-3.48 (m, 1 H), 2.64-2.57 (m, 1 H), 2.15-2.07 (m, 2H), 1.87-1.79 (m, 2H), 1.33-1.11 (m, 4H); m/z (ES+APCI)⁺: 471 [M+H]⁺.

Example 31

ira«s-W-(3-{2-[(5-ChIoro-3-fluoropyridin-2-yl)amino]pyrimidin-5-yI}imidazo[1,2- b]pyridazin-6-yl)cycloh

Following the method for example 16 using 2,5-dichloro-3-fluoropyridine gave a yellow solid (14 mg, 16%); ¹H NMR (400 MHz, DMSO-d_e) δ ppm 9.17 (s, 2H), 8.32 (d, =1.8 Hz, 1 H), 8.09 (dd, J=10.5, 2.3 Hz, 1 H), 7.88 (s, 1 H), 7.75 (d, J=9.6 Hz, 1 H), 7.02 (d, J=6.9 Hz, 1 H), 6.67 (d, J=9.6 Hz, 1H), 3.55-3.45 (m, 1 H), 2.78-2.68 (m, 1 H), 2.16-2.08 (m, 2H), 1.90- 1.81 (m, 2H), 1.32-1.16 (m, 4H); m/z (ES+APCIf: 454/456 [M+Hf. Example 32

frans-W-(3-{2-[(3,5-Difluoropyridin-2-yl)amino]

6-yl)cyclohexane-1 ,4-diamine

Following the method for example 16 using 2-bromo-3,5-difluoropyridine gave a yellow solid (8 mg, 10%); ¹H NMR (400 MHz, DMSO-cf₆) δ ppm 9.15 (s, 2H), 8.33 (d, J=2.7 Hz, 1 H), 8.03-7.95 (m, 1 H), 7.86 (s, 1 H), 7.73 (d, J=9.6 Hz, 1 H), 6.99 (d, J=6.9 Hz, 1 H), 6.66 (d, J=10.1 Hz, 1 H), 3.54-3.45 ( , 1 H), 2.65-2.57 (m, 1 H), 2.13-2.05 (m, 2H), 1.85-1.77 (m, 2H), 1.30-1.07 (m, 4H); m/z (ES+APCI)⁺: 438 [M+H]⁺. Example 33

iraws-W-(3-{2-[(3_>5-Difluoropyridin-2-yl)amino]pyrimidjn-5-yl}imidazo[1,2-b]pyridazin- 6-y!)cyclohexane-1 ,4-diamine

Following the method for example 16 using 2-bromo-3-fluoro-5-(trifluoromethyl)pyridine gave a yellow solid (13 mg, 14%); ¹H NMR (400 MHz, DMSO-d₆) δ ppm 9.26 (s, 2H), 8.61 (s, 1 H), 8.25 (dd, J=10.5, 1.8 Hz, 1H), 7.94 (s, 1 H), 7.75 (d, J=9.6 Hz, 1 H), 7.03 (d, J=6.9 Hz, 1H), 6.68 (d, J=9.6 Hz, 1 H), 3.56-3.46 (m, 1H), 2.65-2.57 (m, 1 H), 2.13-2.05 (m, 2H), 1.86-1.78 (m, 2H), 1.31-1.09 (m, 4H); m/z (ES+APCI)⁺: 488 [M+Hf.

Example 34

frans-/V-(3^2-[(3-Chloropyridin-2-yl)amino]pyri

yl)cyclohexane-1 ,4-diami

Intermediate 3 (100 mg, 0.24 mmol, 1.0 eq), 2,3-dichloropyridine (53 mg, 0.36 mmol, 1.5 eq), Pd(OAc)₂ (11 mg, 0.2 eq), Xantphos (28 mg, 0.2 eq) and Cs₂C0₃ (313 mg, 0.96 mmol, 4.0 eq) in dioxane (1.5 mL) under N₂ were heated at 100°C for 18 h. Additional portions of 2,3-dichloropyridine (0.5 eq), Pd(OAc)₂ (0.1 eq) and Xantphos (0.1 eq) were added and the mixture heated for a further 5 h. The mixture was allowed to cool, then partitioned between CH₂CI₂ (20 mL) and water (20 mL). The organic layer was concentrated under reduced pressure then 4 HCI/dioxane (3 mL) and MeOH (3 mL) were added and the mixture stirred for 6 h. The mixture was concentrated to dryness then purified by prep-HPLC (pH 1) and eluted through an Isolute aminopropyl cartridge (0.5 g) to give a pale yellow solid (3 mg, 3%); ¹H NMR (400 MHz, CD₃OD) δ ppm 9.22 (s, 2H), 8.32 (dd, J=5.0, 1.8 Hz, 1 H), 7.93 (dd, J=8.0, 1.6 Hz, 1 H), 7.82 (s, 1 H), 7.63 (d, J=10.1 Hz, 1 H), 7.19 (dd, J=8.0, 4.8 Hz, 1 H), 6.68 (d, J=10.1 Hz, 1 H), 3.73-3.64 (m, 1 H), 2.87-2.78 (m, 1 H), 2.27-2.20 (m, 2H), 2.04-1.96 (m, 2H), 1.49-1.26 (m, 4H); m/z (ES+APCI)⁺: 436/438 [M+H]⁺.

Example 35

frans-^(3-{2-[(3-Chloropyrazin-2-yl)amino]pyri

yl)cyclohexane-1 ,4-diamine

Following the method for example 34 using 2,3-dichloropyrazine gave a yellow solid (3 mg, 3%); ¹H NMR (400 MHz, CD₃OD) δ ppm 9.27 (s, 2H), 8.34 (d, .7=2.3 Hz, 1H), 8.13 (d, J=2.3 Hz, 1H), 7.85 (s, 1H), 7.63 (d, J=9.6 Hz, 1H), 6.69 (d, J=10.1 Hz, 1H), 3.73-3.63 (m, 1 H), 2.90-2.80 (m, 1H), 2.28-2.20 (m, 2H), 2.05-1.96 (m, 2H), 1.50-1.28 (m, 4H); m/z (ES+APCIf: 437/439 [M+H]⁺.

Example 36

W-(3-Fluoropyridin-2-yI)-5-[6-(piperazin-1-yl)imidazo[1,2-ft]pyridazin-3-yl]pyrimidin-2- amine

a) fert-Butyl 4-(3-bromoimidazo 1 ,2-fa]pyridazin-6-yl)piperazine-1 -carboxylate

Following the method for intermediate 4a using teri-butyl piperazine-1 -carboxylate gave a yellow solid (1.13 g, 33%); ¹H NMR (400 MHz, DMSO-d₆) δ ppm 7.91 (d, J=10.1 Hz, 1H), 7.62 (s, 1H), 7.24 (d, J=10.1 Hz, 1 H), 3.62-3.42 (m, 8H), 1.43 (s, 9H); m/z (ES+APCI)⁺: 382/384 [M+Hf.

b) fert-Butyl 4-[3-(2-aminopyrimidin-5-yl)imidazo[1,2-b]pyridazin-6-yl]piperazine-1- carbox late

₂ Following the method for intermediate 3 using terf-butyl 4-(3-bromoimidazo[1 ,2-b]pyridazin- 6-yl)piperazine-1-carboxylate gave a brown solid (902 mg, 77%); ¹H NMR (400 MHz, DMSO-ofe) δ ppm 8.91 (s, 2H), 7.93 (d, J=9.6 Hz, 1H), 7.90 (s, 1H), 7.20 (d, J=10.1 Hz, 1 H), 6.86 (s, 2H), 3.49 (br. s, 8H), 1.42 (s, 9H); m/z (ES+APCI)⁺: 397 [M+H]⁺.

c) W-(3-Fluoropyridin-2-yl)-5-[6-(piperazin-1 -yl)imidazo[1 ,2-b]pyridazin-3-yl]pyrimidin- 2-amine

To a solution of fe/f-butyl 4-[3-(2-aminopyrimidin-5-yl)imidazo[1 ,2-0]pyridazin-6- yl]piperazine-1-carboxylate (300 mg, 0.76 mmol, 1.0 eq), 2-chloro-3-fluoropyridine (15 mg, 1.14 mmol, 1.5 eq) and Cs₂C0₃ (990 mg, 3.03 mmol, 4.0 eq) in dioxane (10 mL) was added Pd(OAc)_z (50 mg, 0.23 mmol, 0.3 eq) and Xantphos (130 mg, 0.23 mmol, 0.3 eq). The reaction mixture was heated at reflux for 2 h, diluted with DCM (100 mL) and washed with de-ionised water (3 x 100 mL). The combined organics were dried and concentrated in vacuo. Purification by column chromatography (2-20% MeOH/DCM) gave 112 mg of BOC- protected intermediate, which was treated with 4M HCI in dioxane (2 mL). The reaction mixture was basified with triethylamine and concentrated in vacuo. Purification by column chromatography (5-30% MeOH/DCM) gave an off-white solid (45 mg, 15%); ¹H NMR (400 MHz, DMSO-de) δ ppm 10.00 (s, 1H), 9.14 (s, 2H), 8.24 (td, J=4.6, 1.4 Hz, 1 H), 8.00 (s, 1 H), 7.91 (d, J=9.6 Hz, 1 H), 7.75 (ddd, J=10.5, 8.2, 1.4 Hz, 1 H), 7.30 (ddd, J=8.2, 4.6, 3.7 Hz, 1 H), 7.22 (d, J=10.1 Hz, 1 H), 3.47-3.37 (m, 4H), 2.90-2.78 (m, 4H); m/z (ES+APCI)⁺: 392 [M+H]⁺.

Example 37

A/-(3-Fluoropyridin-2-yl)-5-[6-(4-methylpiperazin-1-yl)imidazo[1,2-6]pyridazin-3- yl]pyrimidin-2-amine

Following the method for example 27 using /V-(3-fluoropyridin-2-yl)-5-[6-(piperazin-1- yl)imidazo[1 ,2-b]pyridazin-3-yl]pyrimidin-2-amine (30 mg, 0.08 mmol, 1.0 eq) gave an off- white solid (13 mg, 41%); ¹H NMR (400 MHz, DMSO-d₆) δ ppm 10.00 (s, 1 H), 9.13 (s, 2H), 8.24 (td, J=4.9, 1.2 Hz, 1 H), 8.00 (s, 1 H), 7.93 (d, J=10.1 Hz, 1 H), 7.75 (ddd, J=10.5, 8.0, 1.6 Hz, 1H), 7.30 (ddd, J=8.1 , 4.7, 3.7 Hz, 1 H), 7.25 (d, J=10.1 Hz, 1 H), 3.59-3.44 (m, 4H), 2.48-2.39 (m, 4H), 2.22 (s, 3H); m/z (ES+APCI)⁺: 406 [M+H]⁺.

Example 38

3-{2-[(3-Fluoropyridin-2-yl)amino]pyrimidin-5-yl}-W-[2-(4-methylpiperazin-1- yl)ethyl]imidazo[1 ,2-b]pyridazin-6-amine

a) 3-Bromo-W-[2-(4-methyIpiperazin-1- l)ethyl]imidazo[1,2-£)]pyridazin-6-amine

Following the method for intermediate 4a using 1-(2-aminoethyl)-4-methylpiperazine (1.48 g, 10.32 mmol, 1.2 eq) gave a brown solid (1.17 g, 40%); ¹H NMR (400 MHz, DMSO-cf₆) δ ppm 7.68 (d, J=9.6 Hz, 1 H), 7.47 (s, 1H), 7.05 (t, J=5.3 Hz, 1 H), 6.74 (d, J=9.6 Hz, 1 H), 3.42-3.34 (m, 2H), 2.57-2.51 (m, 2H), 2.50-2.21 (m, 8H), 2.14 (s, 3H); m/z (ES+APCI)⁺: 339/341 [M+H]⁺.

b) 3-(2-Aminopyrimidin-5-yl)-/V-[2-(4-methylpiperazin-1 -yl)ethyl]imidazo[1 ,2- b] py r i dazi n -6-am i n e

Following the method for intermediate 3 using 3-bromo-A/-[2-(4-methylpiperazin-1- yl)ethyl]imidazo[1 ,2-/b]pyridazin-6-amine (1.17 g, 3.45 mmol, 1.0 eq) gave an off-white solid (825 mg, 68%); ¹H NMR (400 MHz, DMSO-d₆) δ ppm 8.93 (s, 2H), 7.76 (s, 1 H), 7.72 (d, J=10.1 Hz, 1H), 7.29-7.05 (m, 1 H), 6.83 (s, 2H), 6.71 (d, =9.6 Hz, 1H), 3.45-3.35 (m, 2H), 3.02-2.52 (m, 13H); m/z (ES+APCI)⁺: 354 [M+H]⁺.

c) 3-{2-[(3-Fluoropyridin-2-yl)amino]pyrimidin-5-yI}-W-[2-(4-methylpiperazin-1- yl)ethyl]imidazo[1 ,2-b]pyridazin-6-amine

Following the method for example 36c using 3-(2-aminopyrimidin-5-yl)-/V-[2-(4- methylpiperazin-1-yl)ethyl]imidazo[1,2-b]pyridazin-6-amine gave, after purification by preparative HPLC, an off-white solid (17 mg, 11%); ¹H NMR (400 MHz, CD₃OD) δ ppm 9.16 (s, 2H), 8.19 (d, .7=4.6 Hz, 1 H), 7.79 (s, 1 H), 7.68-7.59 (m, 2H), 7.23 (ddd, J=8.1 , 4.7, 3.7 Hz, 1 H), 6.73 (d, J=9.6 Hz, 1H), 3.51 (t, J=6.9 Hz, 2H), 2.69-2.63 (m, 2H), 2.72-2.36 (m, 8H), 2.29 (s, 3H); m/z (ES+APCI)⁺: 449 [M+H]⁺.

Example 39

W-(3-Fluoropyridin-2-yl)-5-[6-(piperidin-4-yloxy)imidazo[1,2-b]pyridazin-3- yl]pyrimidin-2-amine

a) ferf-Butyl 4-hydroxypiperidine-1-carboxylate

To a solution of piperidin-4-ol (1 g, 9.8 mmol, 1 eq) in DCM (50 mL) and 1 M aqueous NaHC0₃ (15 mL) was added di-ferf-butyl dicarbonate (2.10 mL, 9.80 mmol, 1.0 eq) at 0°C and allowed to stir at RT for 2 h. The mixture was diluted with EtOAc (50 mL), washed with saturated aqueous citric acid solution (30 mL), the organic layer was dried (Na₂S0 ), concentrated under reduced pressure and purification by silica gel chromatography (0-10% EtOAc pet. ether) gave a colorless liquid (1.2 g, 60%); ¹H NMR (400 MHz, DMSO-d₆) δ ppm 4.70 (d, J=4.4 Hz, 1 H), 3.67-3.58 (m, 2H), 2.93 (br. s, 2H), 1.68-1.64 (m, 2H), 1.47 (s, 9H), 1.38-1.15 (m, 2H).

b) f erf-Butyl 4-(3-bromoimid -ft]pyridazin-6-yloxy)piperidine-1-carboxylate

To a solution of terf-butyl 4-hydroxypiperidine-1-carboxylate (1.04 g, 5.15 mmol, 2.0 eq) in anhydrous THF (10 mL) was added NaH (60% in mineral oil, 206 mg, 5.15 mmol, 1.3 eq) at 0°C and allowed to stir at RT. After 30 min, 3-bromo-6-chloro-imidazo[1 ,2-b]pyridazine (600 mg, 2.57 mmol, 1.0 eq) was added and the mixture was heated at 65°C for 4 h. The mixture was allowed to cool, diluted with EtOAc (50 mL) and washed with water (50 mL) and the combined organic layers were dried (Na₂S0 ), concentrated under reduced pressure and purification by silica gel chromatography (5-10% EtOAc/pet ether) gave a white solid (400 mg, 40%); ¹H NMR (400 MHz, CDCI₃) δ ppm 7.77 (d, J=9.6 Hz, 1 H), 7.59 (s, 1 H), 6.70 (d, J=9.6 Hz, 1 H), 5.28-5.24 (m, 1 H), 3.78-3.76 (m, 2H), 3.39-3.33 (m, 2H), 2.11-2.06 (m, 2H), 1.88-1.83 (m, 2H), 1.46 (s, 9H); m/z (APCI)⁺: 397/399 [M+H]⁺.

c) fert-Butyl 4-(3-(2-aminopyrimidin-5-yl)imidazo[1,2-ft]pyridazin-6-yloxy)piperidine-1- carboxylate

ferf-Butyl 4-(3-bromoimidazo[1 ,2-b]pyridazin-6-yloxy)piperidine-1-carboxylate (400 mg, 1.01 mmol, 1.0 eq), 2-aminopyrimidine-5-boronic acid pinacol ester (334 mg, 1.51 mmol, 1.5 eq), sodium bicarbonate (340 mg, 4.04 mmol, 4.0 eq) in DMF (10 mL) and water (5 mL) was degassed for 30 min with argon, then (A-Phos)₂PdCI₂ (35 mg, 0.05 eq) was added and further degassed for 30 min. The mixture was heated at 100°C for 2 h, allowed to cool to RT, diluted with EtOAc (100 mL), washed with water (3 x 40 mL), the organic layer was dried (Na₂S0₄), concentrated under reduced pressure and washed with diethyl ether to obtain a pale yellow solid (255 mg, 61 %); ¹H NMR (400 MHz, DMSO-d₆) δ ppm 8.90 (s, 2H) 8.07 (d, J=9.6 Hz, 1 H), 8.00 (s, 1 H), 6.95 (s, 2H), 6.88 (d, J=9.6 Hz, 1H), 5.12-5.08 (m, 1 H), 3.72-3.68 (m, 2H), 3.26-3.16 (m, 2H), 2.07-2.05 (m, 2H), 1.73-1.65 (m, 2H), 1.41 (s, 9H); m/z (APCI)^": 410 [M-H]\

d) iert-Butyl 4-(3-(2-(3-fluoropyridin-2-yIamino)pyrimidin-5-yl)imidazo[1,2- i)]pyridazin-6-yloxy)piperidine-1-carboxylate

terf-Butyl 4-(3-(2-aminopyrimidin-5-yl)imidazo[1 ,2-b]pyridazin-6-yloxy)piperidine-1- carboxylate (800 mg, 1.95 mmol, 1.0 eq), 2-chloro-3-fluoropyridine (387 pL, 512 mg, 3.9 mmol, 2.0 eq), Xantphos (110 mg, 0.19 mmol, 0.1 eq) and Cs₂C0₃ (2.54 g, 7 8 mmol, 4.0 eq) in 1 ,4-dioxane (5 mL) was degassed for 30 min using argon. Pd(PPh₃)₄ (225 mg, 0.19 mmol, 0.1 eq) was added and further degassed for 15 min, then heated at 130°C in a sealed tube for 6 h. The mixture was allowed to cool, was diluted with EtOAc (30 mL) and washed with water (30 mL) and the combined organic layers were dried (Na₂S0₄), concentrated under reduced pressure and the crude compound was purified by trituration with chloroform/diethyl ether to obtain a yellow solid (600 mg, 61 %); ¹H NMR (400 MHz, CDCI₃) δ ppm 9.14 (s, 2H), 8.30 (d, J=5.2 Hz, 1 H), 7.89 (t, J=10.0 Hz, 2H), 7.67 (s, 1H), 7.49-7.44 (m, 1 H), 7.09-7.05 (m, 1 H), 6.75 (d, J=9.6 Hz, 1 H), 5.22-5.20 (m, 1 H), 3.72-3.67 (m, 2H), 3.47-3.40 (m, 2H), 2.06-2.01 (m, 2H), 1.87-1.86 (m, 2H), 1.47 (s, 9H); m/z (APCI)^": 505 [M-H]\

e) W-(3-Fluoropyridin-2-yl)-5-(6-{piperidin- -yloxy)imidazo[1,2- ]pyridazin-3- yl)pyrimidin-2-amine

To ie f-butyl 4-(3-(2-(3-fluoropyridin-2-ylamino)pyrimidin-5-yl)imidazo[1 ,2-£>]pyridazin-6- yloxy)piperidine-1-carboxylate (300 mg, 0.59 mmol, 1.0 eq) in CHCI₃ (5 mL) and MeOH (5 mL) was added trifluoroacetic acid (10 mL) at 0°C and the mixture was stirred at RT for 16 h. The solvent was evaporated under reduced pressure, the residue was dissolved in water and washed with EtOAc (50 mL) and CHCI₃ (50 mL). The aqueous layer was neutralized with 2M aqueous NaOH solution (5 mL) and extracted with CHCI₃ (2 x 30 mL). The combined organic layers were washed with brine, dried (Na₂S0₄), concentrated in vacuo and purification by silica gel chromatography (10% MeOH/CHCI₃) gave an off-white solid (105 mg, 43%); ¹H NMR (400 MHz, CDCI₃) δ ppm 9.15 (s, 2H), 8.30 (d, J=4.4 Hz, 1 H), 7.88-7.86 (m, 2H), 7.71 (s, 1 H), 7.49-7.44 (m, 1H), 7.09-7.04 (m, 1 H), 6.75 (d, J=9.6 Hz, 1 H), 5.14-5.10 (m, 1 H), 3.18-3.12 (m, 2H), 2.86-2.80 (m, 2H), 2.12-2.10 (m, 2H), 1.81-1.74 (m, 2H); m/z (APCI)⁺: 407 [M+Hf.

Example 40

W-(3-Fluoropyridin-2-yI)-5-{6-[(1-methylpiperidin-4-yl)oxy]imidazo[1,2-fe]pyridazin-3^ yl}pyrimidin-2-amine a) 3-Bromo-6-{1 -methyl piperidin-4- loxy)imidazo[1 ,2-b]pyrid

To a solution of 1-methylpiperidin-4-ol (375 mg, 3.2 mmol, 1.5 eq) in anhydrous THF (15 ml_) was added NaH (60% in mineral oil, 130 mg, 3.2 mmol, 1.5 eq) at 0°C. The mixture was allowed to stir at RT for 30 min, then 3-bromo-6-chloro-imidazo[1 ,2-fa]pyridazine (500 mg, 2.14 mmol, 1.0 eq) was added and heated to 65°C for 4 h. The mixture was allowed to cool, diluted with EtOAc (100 mL) and washed with water (50 mL). The organic layer was dried (Na₂S0₄), concentrated under reduced pressure and purification by silica gel chromatography (5-10% MeOH/CHCI₃) gave a pale yellow solid (100 mg, 15%); H NMR (400 MHz, DMSO-d_B) δ ppm 8.04 (d, =10.0 Hz, 1 H), 7.74 (s, 1 H), 6.93 (d, J=9.6 Hz, 1 H), 5.04-5.00 (m, 1 H), 2.75-2.65 (m, 2H), 2.32-2.24 (m, 5H), 2.15-2.05 (m, 2H), 1.85-1.75 (m, 2H); m/z (APCIf: 311/313 [M+H]⁺.

b) 5-(6-(1 -Methy!piperidin-4-yloxy)imidazo[1 ,2-6]pyridazin-3-yl)pyrimidin-2 -amine

Following the method for example 39c using 3-bromo-6-(1-methylpiperidin-4- yloxy)imidazo[1 ,2-J ]pyridazine (1.50 g, 4.82 mmol, 1.0 eq) gave a pale yellow solid (700 mg, 44%); H NMR (400 MHz, DMSO-cQ δ ppm 8.93 (s, 2H), 8.06-8.01 (m, 2H), 6.99 (s, 2H), 6.86 (d, J=9.6 Hz, 1 H), 4.95-4.85 (m, 1 H), 2.75-2.65 (m, 2H), 2.19-2.08 (m, 7H), 1.79- 1.74 (m, 2H); m/z (APCI)⁺: 326 [M+H]⁺.

c) W-(3-Fluoropyridin-2-yl)-5-(6-(1-methylpiperidin-4-yloxy)imidazo[1,2-i)]pyridazin-3- yl)pyrimidin-2-amine

Following the method for example 39d using 5-(6-(1-methylpiperidin-4-yloxy)imidazo[1 ,2- Jb]pyridazin-3-yl)pyrimidin-2-amine (300 mg, 0.92 mmol, 1.0 eq) gave a pale yellow solid (165 mg, 42%); ¹H NM (400 MHz, CDCI₃) δ ppm 9.16 (s, 2H), 8.30 (d, J=4.4 Hz, 1 H), 7.87 (d, J=8.2 Hz, 2H), 7.72 (s, 1 H), 7.49-7.44 (m, 1 H), 7.08-7.04 (m, 1 H), 6.75 (d, J=10.0 Hz, 1 H), 5.10-5.00 (m, 1 H), 2.70-2.65 (m, 2H), 2.45-2.35 (m, 2H), 2.33 (s, 3H), 2.13-2.10 (m, 2H), 1.94-1.92 (m, 2H); m/z (APCI)⁺: 421 [M+H]⁺.

Example 41

( S)-/V-(3-Fluoropyridin-2-yl)-5-[6-(pyrrolidin-3-yloxy)imidazo[1,2-b]pyridazin-3- yl]pyrimidin-2-amine

a) (/?S)-terf-Butyl 3-hydroxypyrrolidine-1-carbox late

To a solution of (RS)-3-hydroxypyrrolidine (1.00 g, 11.5 mmol, 1.0 eq) in THF (20 mL) was added Et₃N (1.91 mL, 13.8 mmol, 1.2 eq) followed by a solution of di-ferf-butyl dicarbonate (3.30 mL, 14.9 mmol, 1.3 eq) in THF (10 mL) at 0°C, and the mixture was allowed to stir at RT for 2 h. The mixture was diluted with EtOAc (50 mL) and washed with saturated aqueous citric acid (30 mL). The organic layer was dried (Na₂S0 ) and concentrated under reduced pressure and purification by silica gel chromatography (10% MeOH/CHCI₃) gave a gum (1.7 g, 79%); ¹H NMR (400 MHz, CDCI₃) δ ppm 4.53 (s, 1 H), 3.47-3.33 (m, 4H), 2.01- 1.92 (m, 3H), 1.46 (s, 9H); m/z (APCI)⁺: 132 [M-'Butyl]⁺.

b) (/?S)-fert-Butyl-3-((3-bromoimidazolo [1 ,2-b]pyridazin-6-yloxy)methyl)pyrrolidine-1- carboxylate

To a solution of (RS)-tert-buty\ 3-hydroxypyrrolidine-1-carboxylate (523 mg, 2.80 mmol, 1.3 eq) in dry THF (20 mL) was added NaH (60% in mineral oil, 107 mg, 2.80 mmol, 1.3 eq) at 0°C. After 5 min, 3-bromo-6-chloro-imidazo[1 ,2-b]pyridazine (500 mg, 2.15 mmol, 1.0 eq) was added and the mixture heated at 65°C for 16 h. The mixture was diluted with EtOAc (40 mL), washed with water (40 mL), the organic layer was dried (Na₂S0₄) and concentrated under reduced pressure to give a pale yellow solid (810 mg, 98%); ¹H N R (400 MHz, CDCI₃) δ ppm 7.78 (d, J=8.0 Hz, 1 H), 7.61 (s, 1 H), 6.70 (d, =8.0 Hz, 1 H), 5.65- 5.55 (m, 1H), 3.80-3.70 (m, 1 H), 3.60-3.40 (m, 3H), 2.27 (s, 2H), 1.47 (s, 9H); m/z (APCI)⁺: 383/385 [M+H]⁺.

c) (RS)-ferf-Butyl 3-(3(2-aminopyrimidine-5-yl)imidazo[1 ,2- ]pyridazin-6- yloxy)pyrrolidine-1 -carboxylate

(RS)-te Tf-Butyl-3-((3-bromoimidazolo[1 ,2-fa]pyridazin-6-yloxy)methyl)pyrrolidine-1- carboxylate (810 mg, 2.12 mmol, 1.0 eq), 2-aminopyrimidine-5-boronic acid pinacol ester (609 mg, 2.75 mmol, 1.3 eq), sodium bicarbonate (712 mg, 8.48 mmol, 4.0 eq) in DMF (10 mL) and water (2.5 mL) was degassed for 30 min with argon then (A-Phos)₂PdCI₂ (75 mg, 0.05 eq) was added and the mixture further degassed for 15 min. The mixture was heated at 100°C for 4 h, allowed to cool to RT, diluted with CHCI₃ (50 mL) and washed with water (3 x 40 mL). The organic layer was dried (Na₂S0₄), concentrated under reduced pressure and purification by silica gel chromatography (10% MeOH/CHC!₃) gave a pale yellow solid (400 mg, 47%); ¹H NMR (400 MHz, CDCI₃) δ ppm 8.90 (s, 2H), 7.89-7.86 (m, 1H), 7.19- 7.17 (m, 1H), 6.72 (d, J=8.0 Hz, 1 H), 5.47 (br. s, 1 H), 5.21 (br. s, 2H), 3.71-3.67 (t

3.61-3.44 (m, 3H), 2.60-2.40 (m, 2H), 1.46 (s, 9H); m/z (APCI)⁺: 398 [M+H]⁺.

d) (f?S)-ferf-Butyl 3-(3-(2-(3-fluoropyridin-2-ylam«no)pyrimidin-5-yl)imidazo[1 ,2- ]pyridazin-6-yloxy)pyrrolidin-1-carboxylate

(RS)-feAf-Butyl 3-(3(2-aminopyrimidine-5-yl)imidazo[1 ,2--j]pyridazin-6-yloxy)pyrrolidine-1- carboxylate (450 mg, 1.13 mmol, 1.0 eq), 2-chloro-3-fIuoropyridine (134 μ!_, 178 mg, 1.36 mmol, 1.2 eq), Xantphos (393 mg, 0.6 eq) and Cs₂C0₃ (1.1 g, 3.4 mmol, 3.0 eq) in 1 ,4- dioxane (15 mL) was degassed with argon for 30 min, then Pd(PPh₃)₄ (785 mg, 0.6 eq) was added and further degassed for 15 min. The mixture was heated at 130°C in a sealed tube for 5 h, allowed to cool, diluted with EtOAc (30 mL), washed with water (30 mL), the organic layer was dried (Na₂S0₄) and concentrated under reduced pressure. The crude compound was washed with diethyl ether to obtain a pale yellow solid (220 mg, 39%); ¹H NMR (400 MHz, CDCI₃) δ ppm 9.16 (s, 2H), 8.30 (d, J=4.4 Hz, 1 H), 7.90 (d, J=4.4 Hz, 2H), 7.75 (s, 1 H), 7.47 (t, J=8.0 Hz, 1 H), 7.09-7.06 (m, 1 H), 6.75 (d, J=8.0 Hz, 1 H), 5.55-5.45 (m, 1 H), 3.75-3.54 (m, 4H), 2.40-2.30 (m, 2H), 1.46 (s, 9H); m/z (APCIf: 493 [M+H]⁺.

e) (/?S)-W-(3-FIuoropyridin-2-yl)-5-(6-(pyrro!idin-3-yloxy)imidazo[1,2- ]pyridazin-3- yl)pyrimidin-2-amine

(RS)-tert Butyl 3-(3-(2-(3-fluoropyridin-2-ylamino)pyrimidin-5-yl)imidazo[1 ,2-b]pyridazin-6- yloxy)pyrrolidin-1-carboxylate (200 mg, 0.40 mmol, 1.0 eq) in CHCI₃ (10 mL) was added saturated ethereal HCI (3 mL) at 0°C and allowed to stir at RT for 4 h. Solvent was evaporated completely under reduced pressure, the residue was neutralized with saturated aqueous NaHCO_s solution, extracted with CHCI₃ (2 x 15 mL), the combined organic layers were washed with saturated brine solution (10 mL), dried (Na₂S0₄), concentrated and purification by silica gel chromatography (10% MeOH/CHCI₃) gave yellow solid (95 mg, 59%); ¹H NMR (400 MHz, CDCI₃) δ ppm 9.19 (s, 2H), 8.30 (d, J=4.4 Hz, 1 H), 7.89 (s, 1 H), 7.87 (d, J=10.0 Hz, 1 H), 7.41 (t, J=9.2 Hz, 1 H), 7.08-7.04 (m, 1 H), 6.73 (d J=8.0 Hz, 1H), 5.50-5.40 (m, 1 H), 3.23-3.13 (m, 3H), 3.01-2.91 (m, 1H), 2.28-2.19 (m, 1 H), 2.06-2.01 (m, 1 H); m/z (APCIf: 393 [M+H]⁺.

Example 42

(f?S)-A -(3-Fluoropyridin-2-yl)-5-{6-[(1-methylpyrrolidin-3-yl)oxy]imidazo[1,2- i>]pyridazin-3-yI}pyrimidin-2 -amine

a) ( ?S)-3-Bromo-6-[(1-methylpyrrolidin-3-yl)oxy]imidazo[1,2-i3]pyridazine

Following the method for example 41 b using (RS)-1-methylpyrrolidin-3-ol (565 mg, 5.60 mmol, 1.3 eq) gave a pale yellow solid (1.4 g, crude); H NMR (400 MHz, CDCI₃) δ ppm 7.74 (d, J= 9.6 Hz, 1 H), 7.59 (s, 1 H), 6.73 (d, J=8.0 Hz, 1 H), 5.48-5.44 (m, 1 H), 2.97-2.89 (m, 2H), 2.82-2.78 (m, 1 H), 2.52-2.45 (m, 1H), 2.42 (s, 3H), 2.40-2.34 (m, 1 H), 2.10-2.04 (m, 1 H); m/z (APCI)⁺: 297/299 [M+H]⁺.

b) ( ?S)-5-(6-(1 -Methylpyrrolidin-3-yloxy)imidazo[1 ,2-b]pyridazin-3-yl)pyrimidin-2- amine

Following the method for example 41 c using (RS)-3-bromo-6-[(1-methylpyrrolidin-3- yl)oxy]imidazo[1 ,2-i)]pyridazine (580 mg, 2.10 mmol, 1.0 eq) gave a pale yellow solid (260 mg, 39%); ¹H NMR (400 MHz, CDCI₃) δ ppm 8.93 (s, 2H), 7.84 (d, J=9.2 Hz, 1 H), 7.81 (s, 1 H), 6.75 (d, J=8.0 Hz, 1 H), 5.40-5.35 (m, 1H), 5.22 (br. s, 2H), 3.05-2.97 (m, 2H), 2.70- 2.65 (m, 1 H), 2.42 (s, 3H), 2.35-2.30 (m, 1 H), 2.11-2.03 (m, 2H); m/z (APCI)⁺: 312 [M+H]⁺. c) (RS)-W-(3-FIuoropyridin-2-yl)-5-(6-(1-methylpyrrolidin-3-yloxy)imidazo[1 ,2- b]pyridazin-3-yl)pyrimidin-2-amine

Following the procedure for example 41 d using (f?S)-5-(6-(1-methylpyrrolidin-3- yloxy)imidazo[1 ,2-b]pyridazin-3-yl)pyrimidin-2-amine (130 mg, 0.42 mmol, 1.0 eq) gave a pale yellow solid (90 mg, 53%); ¹H NMR (400 MHz, CDCI₃) δ ppm 9.18 (s, 2H), 8.30 (d, J=4.4 Hz, 1H), 7.88 (s, 1 H), 7.86 (d, J=9.6 Hz, 1 H), 7.74 (s, 1 H), 7.47 (t, J=8.0 Hz, 1 H), 7.07 (m, 1 H), 6.78 (d, J=8.0 Hz, 1 H), 5.45-5.40 (m, 1 H), 3.04-2.94 (m, 2H), 2.70-2.65 (m, 1 H), 2.51-2.43 (m, 1 H), 2.41 (s, 3H), 2.36-2.27 (m, 1 H), 2.11-2.04 (m, 1H); m/z (APCI)⁺: 325 [M+H]⁺.

Example 43

(f?S)-3-{2-[(3-Fluoropyridin-2-yl)amino]pyrimidin-5^

6]pyridazin-6-amine a) ( ?S)-ierf-ButyI S-KS-bromoimidazoil^-feJpyridazin-e-ylJaminolpiperidine-l - carboxylate

Following the method for intermediate 4a using (RS)-terf-butyl 3-aminopiperidine-1- carboxylate (2.07 g, 10.32 mmol, 1.2 eq) gave a yellow solid (731 mg, 21 %); ¹H NMR (400 MHz, DMSO-d₆) δ ppm 7.72 (d, J=9.6 Hz, 1 H), 7.48 (s, 1 H), 7.05 (d, J=6.0 Hz, 1 H), 6.75 (d, J=9.6 Hz, 1 H), 3.83-3.63 (m, 2H), 3.61-3.43 (m, 1 H), 3.41-3.23 (m, 1 H), 2.03-1.88 (m, 1 H), 1.88-1.70 (m, 1 H), 1.70-1.52 (m, 1 H), 1.51-1.05 (m, 11 H); m/z (ES+APCI)⁺: 396/398 [M+H]⁺.

b) (/?S)-ierf-Butyl 3-{[3-(2-aminopyrimidin-5-yl)imidazo[1,2-f)]pyridazin-6- yl]amino}piperidine-1 -carbox late

Following the method for intermediate 3 using (RS)-terf-butyl 3-[(3-bromoimidazo[1 ,2- b] pyridazin-6-yl)amino]piperidine-1-carboxylate (731 mg, 1.84 mmol, 1.0 eq) gave a brown solid (532 mg, 70%); ¹H NMR (400 MHz, DMSO-d₆) δ ppm 8.94 (s, 2H), 7.81-7.71 (m, 1 H),

7.62-7.44 (m, 1 H), 6.99 (d, J=6.0 Hz, 1 H), 6.81 (br. s, 2H), 6.70 (d, J=9.6 Hz, 1 H), 3.69- 3.56 (m, 2H), 3.54-3.35 (m, 1H), 3.30-3.12 (m, 1H), 2.07-1.91 (m, 1 H), 1.88-1.70 (m, 1 H), 1.70-1.52 (m, 1 H), 1.50-0.95 (m, 11 H); (ES+APCI)⁺: 411 [M+H]⁺.

c) (RS)-3-{2-[(3-Fluoropyridin-2-yI)amino]pyrimidin-5-yl}-/V-(piperidin-3- yl)imidazo[1,2-/j]pyridazin-6-amine

Following the method for example 36c using (RS)-te i-butyl 3-{[3-(2-aminopyrimidin-5- yl)imidazo[1 ,2-b]pyridazin-6-yl]amino}piperidine-1-carboxylate (500 mg, 1.22 mmol, 1.0 eq), purification by preparative HPLC gave an off-white solid (44 mg, 9%); ¹H NMR (400 MHz, CD₃OD) δ ppm 9.19 (s, 2H), 8.34-8.09 (m, 1 H), 7.81 (s, 1 H), 7.68-7.58 (m, 2H), 7.22 (ddd, J=8.1 , 4.7, 3.7 Hz, 1 H), 6.71 (d, J=9.6 Hz, 1 H), 3.90-3.76 (m, 1 H), 3.37-3.30 (m, 1 H), 2.99- 2.88 (m, 1 H), 2.67-2.54 (m, 1H), 2.54-2.43 (m, 1 H), 2.19-2.04 (m, 1 H), 1.86-1.73 (m, 1 H), 1.71-1.47 (m, 2H); m/z (ES+APCI)⁺: 406 [M+H]⁺. Example 44

(/?S)-3-{2-[(3-Fluoropyridin-2-yl)amino]pyrimidin-5-yl}-Ai-(1-methylpiperidin-3- yl)imidazo[1,2-6]pyridazin-6-amine

Following the method for example 27 using (RS)-3-{2-[(3-fluoropyridin-2- yl)amino]pyrimidin-5-yl}-/\/-(piperidin-3-yl)imidazo[1 ,2-i ]pyridazin-6-amine (30 mg, 0.08 mmol, 1.0 eq) gave an off-white solid (12 mg, 39%); ¹H NMR (400 MHz, CD₃OD) δ ppm 9.12 (s, 2H), 8.18 (d, J=5.0 Hz, 1H), 7.78 (s, 1 H), 7.68-7.57 (m, 2H), 7.22 (ddd, J=8.4, 4.9, 3.7 Hz, 1 H), 6.72 (d, J=10.1 Hz, 1 H), 4.04-3.88 (m, 1 H), 3.08-2.95 (m, 1H), 2.74-2.57 (m, 1 H), 2.29 (s, 3H), 2.26-2.09 (m, 2H), 2.09-1.95 (m, 1 H), 1.87-1.76 (m, 1 H), 1.76-1.62 (m, 1 H), 1.50-1.32 (m, 1 H); m/z (ES+APCI)⁺: 420 [M+H]⁺. Example 45

3-{2-[(3-Fluoropyridin-2-y!)amino]pyrimidin-5-yl}-W-[2-(pyrroIidin-1- yl)ethyl]imidazo[1,2-i»Jpyridazin-6-amine

a) 3-Bromo-A/-[2-(pyrroIidin-1-yl ethyI]imidazo[1,2-J ]pyridazin-6-amine

3-Bromo-6-chloro-imidazo[1 ,2-b]pyridazine (500 mg, 2.15 mmol, 1.0 eq), 1 ,2- aminoethylpyrrolidine (682 μΙ_, 614 mg, 5.38 mmol, 2.5 eq) and NMP (3 mL) were heated at 170°C under microwave irradiation for 60 min. The mixture was diluted with EtOAc (60 mL) and washed with water (50 mL). The aqueous layer was basified to pH 10 with 2M NaOH (aq.), extracted with EtOAc (40 mL) and the combined organic layers were dried and concentrated under reduced pressure. Purification by silica gel chromatography (2- 20% MeOH/EtOAc with 1 % concentrated aqueous ammonia) gave a yellow solid (450 mg, 68%); H NMR (400 MHz, DMSO-cfe) δ ppm 7.67 (d, J=9.6 Hz, 1H), 7.46 (s, 1 H), 7.11 (t, J=5.3 Hz, 1H), 6.75 (d, J=9.6 Hz, 1 H), 3.42-3.35 (m, 2H), 2.66 (t, J=6.6 Hz, 2H), 2.54-2.49 (m, 4H), 1.72-1.65 (m, 4H); m/z (ESf: 310/312 [M+H]⁺.

b) 3-(2-Aminopyrimidin-5-yl)-W-[2-(pyrrolidin-1-yI)ethyl]imidazo[1,2-b]pyridazin-6- amine

Following the procedure for intermediate 3 using 3-bromo-/S/-[2-(pyrrolidin-1- yl)ethyl]imidazo[1 ,2-Jb]pyridazin-6-amine (443 mg, 1.43 mmol, 1.0 eq) gave an off-white solid (421 mg, 91 %); ¹H NMR (400 MHz, DMSO-d₆) δ ppm 8.93 (s, 2H), 7.78-7.72 (m, 2H), 7.15 (br. s, 1 H), 6.83 (s, 2H), 6.70 (d, J=9.6 Hz, 1 H), 3.45 (br. s, 2H), 3.09-2.61 (m, 6H), 1.85-1.70 (m, 4H); m/z (ES)⁺: 325 [M+H]⁺.

c) 3-{2-[(3-Fluoropyridin-2-yl)amino]pyrimidin-5-yI}-W-[2-(pyrrolidin-1- yl)ethyl]imidazo[1 ,2-b]pyridazin-6-amine

3-(2-Aminopyrimidin-5-yl)-A/-[2-(pyrrolidin-1 -yl)ethyl]imidazo[1 ,2-6]pyridazin-6-amine (100 mg, 0.31 mmol, 1.0 eq), 2-chloro-3-fluoropyridine (43 μΙ_, 57 mg, 0.43 mmol, 1.4 eq), Pd(OAc)₂ (12 mg, 0.2 eq), Xantphos (36 mg, 0.2 eq) and Cs₂C0₃ (404 mg, 1.24 mmol, 4.0 eq) in dioxane (1.5 mL) under N₂ were heated at 100°C for 5 h. The mixture was allowed to cool, then concentrated under reduced pressure, and purification by silica gel chromatography (3-30% MeOH/EtOAc with 1 % concentrated aqueous ammonia) gave a pale yellow solid (78 mg, 60%); H NMR (400 MHz, DMSO-cf₆) δ ppm 9.97 (s, 1 H), 9.17 (s, 2H), 8.24 (td, J=5.0, 1.4 Hz, 1 H), 7.89 (s, 1 H), 7.77-7.70 (m, 2 H), 7.32-7.27 (m, 1 H), 7.10 (t, J=5.5 Hz, 1 H), 6.76 (d, J=9.6 Hz, 1 H), 3.41-3.33 (m, 2H), 2.67 (t, J=6.9 Hz, 2H), 2.48- 2.45 (m, 4H), 1.70-1.63 (m, 4H); m/z (ES)⁺: 420 [M+H]⁺.

Example 46

( ?S)-3-{2-t(3-Fluoropyridin-2-yl)amino]pyrimidin-5-yl}-W-(pyrrolidin-3-y()imidazo[1,2- J ]pyridazin-6-amine

a) (ftS)-ferf-Butyl 3-[(3-bromoimidazo[1,2- ]pyridazin-6-yl)amino]pyrrolidine-1- carboxylate

3-Bromo-6-chforo-imidazo[1 ,2-/b]pyridazine (1.00 g, 4.30 mmol, 1.0 eq), (f?S)-3-amino-1-/V- Boc-pyrrolidine (2.00 g, 2.5 eq) and NMP (4 mL) were heated at 140°C for 16 h. The mixture was diluted with EtOAc (80 mL) and washed with water (60 mL). The aqueous layer was extracted with EtOAc (30 mL) and the combined organic layers were dried and concentrated under reduced pressure. Purification by silica gel chromatography (0.2-3.5% MeOH/EtOAc) gave a brown-yellow solid (588 mg, 36%); ¹H NMR (400 MHz, DMSO-d_B) δ ppm 7.73 (d, J=9.6 Hz, 1H), 7.50 (s, 1 H), 7.45-7.38 (m, 1H), 6.71 (d, J=9.6 Hz, 1 H), 4.31- 4.20 (m, 1 H), 3.73-3.58 (m, 1 H), 3.42-3.13 (m, 3H), 2.21-2.12 (m, 1 H), 1.95-1.83 (i 1.43-1.36 (m, 9H).

b) (RS)-fert-Butyl S-iP-iZ-arninopyrimidin-S-ylJimidazotl^-ijJpyridazin-S- yl]amino}pyrrolidine-1-carbox Iate

Following the method for intermediate 3 using (RS)-tert-buty\ 3-[(3-bromoimidazo[1 ,2- b] pyridazin-6-yl)amino]pyrrolidine-1-carboxylate gave a pale yellow solid (272 mg, 45%); ¹H NMR (400 MHz, DMSO-cf₆) δ ppm 8.94 (d, J=7.8 Hz, 2H), 7.81-7.73 (m, 2H), 7.35-7.28 (m, 1 H), 6.84 (br. s, 2H), 6.66 (d, J=9.6 Hz, 1 H), 4.26-4.19 (m, 1 H), 3.68-3.46 (m, 1 H), 3.41-3.34 (m, 2H), 3.30-3.18 (m, 1 H), 2.21-2.06 (m, 1 H), 2.04-1.87 (m, 1 H), 1.39 (d, J=12.8 Hz, 9H); m/z (ESf: 397 [M+H]⁺.

c) (ftS)-iert-Butyl 3-[(3-{2-[(3-fluoropyridin-2-yl)amino]pyrimidin-5-yl}imidazo[1 ,2- i)]pyridazin-6-yl)amino] rrolidine-1 -carboxylate

Following the method for example 45c using (RS)-tert-bu\y\ 3-{[3-(2-aminopyrimidin-5- yl)imidazo[1 ,2-)b]pyridazin-6-yl]amino}pyrrolidine-1-carboxylate gave a pale yellow solid (68 mg, 55%); ¹H NMR (400 MHz, DMSO-d_B) δ ppm 9.99 (br. s, 1H), 9.17-9.08 (m, 2H), 8.25- 8.20 (m, 1 H), 7.90 (s, 1 H), 7.81 (d, J=10.1 Hz, 1 H), 7.77-7.69 (m, 1 H), 7.41-7.34 (m, 1 H), 7.33-7.24 (m, 1 H), 6.72 (d, J=10.1 Hz, 1 H), 4.30-4.20 (m, 1H), 3.71-3.46 (m, 1 H), 3.40-3.35 (m, 2H), 3.30-3.15 (m, 1H), 2.20-2.08 (m, 1H), 2.02-1.92 (m, 1H), 1.43-1.31 (m, 9H); m/z (ES)⁺: 397 [M+H]⁺.

d) ( ?S)-3-{2-[(3-Fluoropyridin-2-yl)amino]pyrirnidin-5-yl}-W-(pyrroIidin-3- yl)imidazo[1,2-b]pyridazin-6-amine

(RS)-ferf-Butyl 3-[(3-{2-[(3-fluoropyridin-2-yl)amino]pyrimidin-5-yl}imidazo[1 ,2-6]pyridaz yl)amino]pyrrolidine-1-carboxylate (67 mg, 0.14 mmol, 1.0 eq) was stirred with 4M HCI/dioxane (1.5 mL) and MeOH (1.5 mL) for 5 h. The mixture was concentrated under reduced pressure, then dissolved in MeOH/CH₂CI₂ and eluted through an Isolute aminopropyl cartridge (1 g) to give a beige solid (52 mg, 98%); ¹H NMR (400 MHz, DMSO- d₆) δ ppm 9.99 (br. s, 1 H), 9.20-9.12 (m, 2H), 8.26-8.20 (m, 1 H), 7.89 (s, 1 H), 7.78-7.71 (m, 2H), 7.32-7.26 (m, 1 H), 7.23 (d, J=6.0 Hz, 1H), 6.69 (d, J=9.6 Hz, 1 H), 4.16-4.08 (m, 1 H), 3.10 (dd, J=11.4, 6.4 Hz, 1H), 2.95-2.72 (m, 3H), 2.10-2.00 (m, 1H), 1.73-1.63 (m, 1 H); m/z (ES)⁺: 392 [M+H]⁺.

Example 47

(RS)-3-{2-[(3-FIuoropyridin-2-yl)amino]pyrimidin-5-yI}-/V-(1-methylpyrrolidin-3- yl)imidazo[1,2-b]pyridazin-6-amine

(f?S)-3-{2-[(3-Fluoropyridin-2-yl)amino]pyrimidin-5-yl}-A/-(pyrrolidin-3-yl)imidazo[1 ,2- 6]pyridazin-6-amine (21 mg, 0.054 mmol, 1.0 eq) was dissolved in THF (0.5 mL) then AcOH (6.1 pL, 0.11 mmol, 2.0 eq), formaldehyde (37% aqueous, 4.1 pL, 0.054 mmol, 1.0 eq) and sodium triacetoxyborohydride (23 mg, 0.11 mmol, 2.0 eq) were added. After 1 h, saturated aqueous NaHC0₃ was added and the mixture concentrated to dryness under reduced pressure. Purification by silica gel chromatography (3-30% MeOH/EtOAc with 1 % cone, aqueous ammonia) gave a white solid (8 mg, 37%); H NMR (400 MHz, CD₃OD) δ ppm 9.15 (s, 2H), 8.19 (d, J=5.0 Hz, 1 H), 7.82 (s, 1 H), 7.71-7.59 (m, 2H), 7.26-7.19 (m, 1 H), 6.76 (d, J=9.6 Hz, 1 H), 4.46-4.37 (m, 1H), 3.27-3.20 (m, 1 H), 3.14-3.03 (m, 1 H), 3.01- 2.93 (m, 1 H), 2.92-2.83 (m, 1 H), 2.59 (s, 3H), 2.55-2.42 (m, 1 H), 2.03-1.91 (m, 1 H); m/z (ES)⁺: 406 [M+H]⁺.

Example 48

W-(3-Fluoropyridin-2-yl)-5-{6-[2-(4-methylpiperazin-1 -yI)ethoxy]imidazo[1,2- fa]pyridazin-3-yl}pyrimidin-2-amine

a) 3-Bromo-6-(2-(4-methylpiperazin-1 - l)ethoxy)imidazo[1 ,2-6]pyridazine

To a solution of 2-(4-methylpiperazin-1-yl)ethanol (4.60 g, 32.2 mmol, 1.5 eq) in anhydrous THF (50 mL) was added NaH (60% in mineral oil, 1.00 g, 42.9 mmol, 2.0 eq) at 0°C and the mixture was stirred at RT. After 1 h, 3-bromo-6-chloro-imidazo[1 ,2-j ]pyridazine (500 mg, 2.14 mmol, 1 eq) was added at 0°C. The mixture was heated to 65°C for 2 h, then allowed to cool, poured into crushed ice and the precipitated solid was collected by filtration to obtain an off-white solid (4.5 g, 62%); H NMR (400 MHz, DMSO-d_B) δ ppm 8.04 (d, J=10.0 Hz, 1 H), 7.74 (s, 1 H), 6.96 (d, J=9.6 Hz, 1 H), 4.46 (t, J=11.6 Hz, 2H), 3.40- 3.30 (m, 4H), 2.74 (t, J=11.6 Hz, 2H), 2.32-2.28 (m, 4H), 2.12 (s, 3H); m/z (APCI)⁺: 340/342 [M+H]⁺.

b) 5-(6-(2-(4- ethylpiperazin-1 -yl)ethoxy)imidazo[1 ,2-b]pyridazin-3-yl)pyrimidin-2- amine

Following the method for example 39c using 3-bromo-6-(2-(4-methylpiperazin-1- yl)ethoxy)imidazo[1 ,2-b]pyridazine (1.50 g, 4.42 mmol, 1.0 eq) gave a pale yellow solid (500 mg, 32%); ¹H NMR (400 MHz, CD₃OD) δ ppm 8.90 (d, J=2.8 Hz, 2H), 7.92-7.86 (m, 2H), 6.92-6.89 (m, 1H), 4.52-4.50 (m, 2H), 2.89-2.86 (m, 2H), 2.65-2.51 (m, 8H), 2.28 (s, 3H); m/z (APCI)⁺: 355 [M+H]⁺.

c) /V-(3-Fluoropyridin-2-yl)-5-(6-(2-(4-methylpiperazin-1 -yl)ethoxy)imidazo[1 ,2- ]pyridazin-3-yl)pyrimidin-2-amine

5-(6-(2-(4-Methylpiperazin-1-yl)ethoxy)imidazo[1 ,2-b]pyridazin-3-yl)pyrimidin-2-am (500 mg, 1.41 mmol, 1.0 eq), 2-chloro-3-fluoropyridine (279 μΙ_, 370 mg, 1.2 mmol, 2 eq), Xantphos (82 mg, 0.1 eq) and Cs₂C0₃ (1.83 g, 5.64 mmol, 4.0 eq) in 1 ,4-dioxane (15 mL) was degassed for 30 min using argon. Pd(PPh₃) (106 mg, 0.1 eq) was added and further degassed for 15 min, then heated at 130°C in a sealed tube for 6 h. The mixture was allowed to cool, diluted with CHCI₃ (40 mL), washed with water (30 mL), the organic layer was dried (Na₂S0₄), concentrated under reduced pressure and washed with diethyl ether to obtain a pale yellow solid (90 mg, 14%); ¹H NMR (400 MHz, CDCI₃) δ ppm 9.21 (s, 2H), 8.31 (d, J=4.8 Hz, 1 H), 7.90-7.86 (m, 2H), 7.75 (s, 1 H), 7.49-7.44 (m, 1 H), 7.08-7.05 (m, 1 H), 6.81 (d, J=10.0 Hz, 1 H), 4.48 (t, J=10.8 Hz, 2H), 2.86 (t, J=10.8 Hz, 2H), 2.61-2.48 (m, 8H), 2.29 (s, 3H); m/z (APCI)⁺: 450 [M+H]⁺.

Example 49

A -(3-Fluoropyridin-2-yl)-5-{6-[2-(pyrrolidin-1 -yl)ethoxy]imidazo[1,2-b]pyridazin-3- yi}pyrimidin-2-amine

a) 3-Bromo-6-(2-(pyrrolidin-1 -yl ethoxy)imidazo[1 ,2-b]pyridazine

Following the method for example 41 b using 2-(pyrrolidin-1-yl)ethanol (1.19 g, 10.34 mmol, 1.2 eq) gave a brown solid (2.60 g, 97%); ¹H NMR (400 MHz, CDCI₃) δ ppm 7.75 (d, J=8.0 Hz, 1 H), 7.59 (s, 1 H), 6.78 (d, J=8.0 Hz, 1 H), 4.55 (t, J=6.0 Hz, 2H), 2.95 (t, J=6.0 Hz, 2H),

2.70-2.60 (m, 4H), 1.84-1.82 (m, 4H); m/z (APCI)⁺: 311/313 [M+H]⁺.

b) 5^6-[2-(Pyrrolidin-1-yl)ethox imidazo[1,2- j]pyridazin-3-yl}pyrimidin-2-ami

Following the method for example 39c using 3-bromo-6-(2-(pyrrolidin-1- yl)ethoxy)imidazo[1 ,2-b]pyridazine (1.50 g, 4.83 mmol, 1.0 eq) gave an off-white solid (620 mg, 39%); Ή NMR (400 MHz, CDCI₃) δ ppm 8.94 (s, 2H), 7.85-7.82 (m, 2H), 6.80 (d, J=8.0 Hz, 1 H), 5.19 (br. s, 2H), 4.47 (t, J=5.6 Hz, 2H), 2.95 (t, J=6.0 Hz, 2H), 2.70-2.60 (m, 4H), 1.90-1.80 (m, 4H); m/z (APCI)^": 324 [M-H]\

c) 3-Fluoro-N-(4-(6-(2-(pyrroIidin-1 -yl)ethoxy)imidazo[1 ,2-b]pyridazin-3- yl)phenyl)pyridin-2-amine

5-{6-[2-(Pyrrolidin-1-yl)ethoxy]imidazo[1 ,2-b]pyridazin-3-yl}pyrimidin-2-amine (300 mg, 0.92 mmol, 1.0 eq), 2-chloro-3-fluoropyridine (127 μΙ_, 157 mg, 1.20 mmol, 1.3 eq), Xantphos (53.4 mg, 0.1 eq) and Cs₂C0₃ (902 mg, 2.76 mmol, 3.0 eq) in dioxane (15 mL) were degassed for 30 min using argon, then Pd(PPh₃)₄ (106 mg, 0.1 eq) was added and further degassed for 15 min. The mixture was heated at 130°C in sealed tube for 5 h, then allowed to cool, diluted with EtOAc (40 mL) and washed with water (30 mL). The organic layer was dried (Na₂S0 ), concentrated under reduced pressure and purification by chromatography on alumina (3% MeOH/CHCI₃) gave a pale yellow solid (220 mg, 56%); ¹H NMR (400 MHz, CDCI₃) δ ppm 9.22 (s, 2H), 8.31 (d, J=4.0 Hz, 1 H), 7.90 (s, 1 H), 7.87 (t, J=9.6 Hz, 1 H), 7.71 (s, 1 H), 7.49-7.44 (m, 1 H), 7.08-7.03 (m, 1 H), 6.84 (d, J=8.0 Hz, 1 H), 4.49 (t, J=8.0 Hz, 2H), 2.95 (t, J=8.0 Hz, 2H), 2.66-2.60 (m, 4H), 1.85-1.80 (m, 4H); m/z (APCI)⁺: 421 [M+H]⁺.

Example 50

(/?S)-Af-(3-fIuoropyridin-2-yl)-5-{6-[(1-methylpyrrolidin-2-yl)methoxy]imidazo[1,2- ]pyridazin-3-yl}pyrimidin-2-amine

a) (/?S)-(1 -Methylpyrrolidin-2-yl)methanoI

A mixture of (RS)-pyrrolidin-2-ylmethanol (1.00 g, 9.90 mrnol, 1.0 eq), formaldehyde (35% aqueous, 10 mL) and 10% Pd/C (200 mg) was stirred under a balloon of hydrogen gas for 18 h. The mixture was filtered through a Celite pad, concentrated under reduced pressure and purification by silica gel chromatography (20% MeOH/CHCI₃) gave a colorless liquid (650 mg, 56%); ¹H NMR (400 MHz, CDCI₃) 6 ppm 3.65 (dd, =10.0, 3.6 Hz, 1 H), 3.43 (dd, J=10.8, 2.0 Hz, 1H), 3.10-3.05 (m, 1 H), 2.40-2.35 (m, 1 H), 2.33 (s, 3H), 2.32-2.25 (m, 1 H), 1.93-1.68 (m, 4H); m/z (APCIf: 116 [M+H]⁺.

b) ( ?S)-3-Bromo-6-((1-methyIpyrrolidin-2- I)methoxy)imidazo[1,2-b]pyridazine

Following the method for example 41b using (RS)-(1-methylpyrrolidin-2-yl)methanol (644 mg, 5.60 mrnol, 1.3 eq) gave a colorless liquid (1.38 g, crude); ¹H NMR (400 MHz, CDCI₃) δ ppm 7.75 (d, J=9.6 Hz, 1 H), 7.59 (s, 1 H), 6.76 (d, J=8.0 Hz, 1 H), 4.46 (dd, J=11.2, 4.8 Hz, 1 H), 4.35 (dd, J=11.2, 5.2 Hz, 1 H), 3.13 (t, J=8.0 Hz, 1 H), 2.71-2.68 (m, 1 H), 2.50 (s, 3H), 2.34-2.27 (m, 1 H), 2.05-2.02 (m, 1 H), 1.88-1.75 (m, 3H); m/z (APCI)⁺: 311/313 [M+Hf. c) (/?S)-5-(6-((1-Methylpyrrolidin-2-yl)methoxy)imidazo[1,2-b]pyridazin-3-yl)pyrimidin- 2-amine

Following the method for example 39c using (f?S)-3-bromo-6-((1-methylpyrrolidin-2- yl)methoxy)imidazo[1 ,2-b]pyridazine (1.38 g, 4.45 mmol, 1.0 eq) gave an off-white solid (650 mg, 45%); ¹H NMR (400 MHz, CDCI₃) δ ppm 8.94 (s, 2H), 7.86-7.81 (m, 2H), 6.78 (d. J=8.0 Hz, 1 H), 5.26 (br. s, 2H), 4.38-4.28 (m, 2H), 3.14 (t, J=7.2 Hz, 1 H), 2.70-2.64 (m, 1 H), 2.46 (s, 3H), 2.34-2.27 (m, 1 H), 2.05-1.96 (m, 1 H), 1.85-1.76 (m, 3H); m/z (APCIf: 326 [M+H]⁺.

d) (/?S)-A/-(3-Fluoropyridin-2-yI)-5-(6-((1-methylpyrrolidin-2-yl)methoxy)imidazo[1,2- b]pyridazin-3-yl)pyrimidin-2-amine

Following the method for example 49c using (ftS)-5-(6-((1-methylpyrrolidin-2- yl)methoxy)imidazo[1 ,2-b]pyridazin-3-yl)pyrimidin-2-amine (300 mg, 0.92 mmol, 1.0 eq) gave a pale yellow solid (270 mg, 69%); ¹H NMR (400 MHz, CDCI₃) δ ppm 9.21 (s, 2H), 8.30 (d, J=4.4 Hz, 1 H), 7.89-7.85 (m, 2H), 7.77 (s, 1 H), 7.46 (t, .7=8.0 Hz, 1 H), 7.08-7.04 (m, 1 H), 6.82 (d, J=8.0 Hz, 1 H), 4.36-4.32 (m, 2H), 3.14 (t, J=8.0 Hz, 1 H), 2.68-2.65 (m, 1 H), 2.46 (s, 3H), 2.32-2.27 (m, 1 H), 2.02-1.98 (m, 1 H), 1.88-1.76 (m, 3H); m/z (APCI)⁺: 421 [M+H]⁺.

Example 51

3-{2-[(3-Fluoropyridin-2-yl)amino]pyrimidin-5-yl}-W-[2-(morphoIin-4- yl)ethyl]imidazo[1,2-b]pyridazin-6-amine

a) 3-Bromo-W 2-(morphoIin-4-yl)ethyl]imidazo[1,2-i)]pyridazin-6-amine

Following the method for intermediate 4a using 2-(morpholin-4-yl)ethanamine (2.00 g, 15.5 mmol, 1.2 eq), gave a yellow oil (1.73 g, 41%); ¹H NMR (400 MHz, DMSO-cf₆) δ ppm 7.69 (d, J=9.6 Hz, 1H), 7.47 (s, 1 H), 7.09 (t, J=5.5 Hz, 1 H), 6.74 (d, J=9.6 Hz, 1 H), 3.64-3.49 (m, 4H), 3.45-3.36 (m, 2H), 2.54 (t, J=6.6 Hz, 2H), 2.48-2.39 (m, 4H); m/z (ES+APCI)⁺: 326/328 [M+H]⁺.

b) 3-(2-Aminopyrimidin-5-yI)-/V-[2-(morpho!in-4-yl)ethyI]imidazo[1,2-ft]pyridazin-6- amine

Following the method for intermediate 3 using 3-bromo-/V-[2-(morpholin-4- yI)ethyl]imidazo[1 ,2-/j]pyridazin-6-amine (1.70 g, 5.21 mmol, 1.0 eq) gave an off-white solid (1.62 g, 91 %); ¹H NMR (400 MHz, DMSO-d₆) δ ppm 8.93 (s, 2H), 7.76 (s, 1 H), 7.71 (d, J=9.6 Hz, 1 H), 7.03 (t, J=5.3 Hz, 1 H), 6.83 (s, 2H), 6.70 (d, J=9.6 Hz, 1 H), 3.58 (t, J=4.4 Hz, 4H), 3.43-3.31 (m, 2H), 2.55 (t, 7=6.6 Hz, 2H), 2.47-2.34 (m, 4H); m/z (ES+APCI)⁺: 341 [M+H]⁺.

c) 3-{2-[(3-F!uoropyridin-2-y!)amirio]pyrimidin-5-yl}-Af-[2-(inorpholin-4- yl)ethyl]imidazo[1 ,2-b]pyridazin-6-amine

Following the method for example 36c using 3-(2-aminopyrimidin-5-yl)-A/-[2-(morpholin-4- yl)ethyl]imidazo[1 ,2-b]pyridazin-6-amine (106 mg, 0.31 mmol, 1.0 eq), purification by preparative HPLC gave an off-white solid (44 mg, 32%); H NMR (400 MHz, DMSO-d₆) δ ppm 9.97 (s, 1 H), 9.16 (s, 2H), 8.23 (td, J=4.6, 1.4 Hz, 1 H), 7.88 (s, 1 H), 7.79-7.69 (m, 2H), 7.30 (ddd, J=8.2, 4.6, 3.7 Hz, 1 H), 7.09 (t, J=5.5 Hz, 1 H), 6.74 (d, J=9.6 Hz, 1 H), 3.59-3.49 (m, 4H), 3.44-3.34 (m, 2H), 2.54 (t, J=6.6 Hz, 2H), 2.47-2.35 (m, 4H); m/z (ES+APCI)⁺: 436 [M+H]⁺.

Example 52

3-(2-(3-F!uoropyridin-2-ylarnino)pyrsmidin-5-yl)-N-(4-morphoIino-trans- cyclohexyl)imidazo[1,2-b]pyridazin-6-amine

a) 3-Bromo-N-(4-morpholino-trans-c clohexyI)imidazo[1,2-b]pyridazin-6-amine

To a stirred solution of frans-/V-(3-bromo-imidazo[1 ,2-/3]pyridazin-6-yl)-cyclohexane-1 ,4- diamine (1.0 g, 3.24 mmol, 1.0 eq) in n-BuOH (15 mL) was added ₂C0₃ (2.2 g, 15.94 mmol, 5.0 eq) and potassium iodide (1.18 g, 7.11 mmol, 2.2 eq) at 0°C. After 15 min, 1- chloro-2-(2-chloroethoxy)ethane (925 mg, 6.47 mmol, 2.0 eq) was added and the reaction mixture was heated at 100°C for 16 h. The reaction mixture was cooled to RT and filtered. The filtrate was diluted with dichioromethane (50 mL), washed with H₂0 (2 x 20 mL) and brine solution (20 mL). The organic layer was dried (Na₂S0₄), concentrated and purification by silica gel chromatography (5% MeOH/CHCI₃) gave a yellow solid (600 mg, 49%); H NMR (400MHz, CDCI₃) δ ppm 7.58 (d, J=10.0 Hz, 1 H), 7.47 (s, 1 H), 6.40 (d, J=9.6 Hz, 1H), 4.27 (d, J=6.8 Hz, 1 H), 3.75-3.69 (m, 5H), 2.60-2.55 (m, 4H), 2.40-2.20 (m, 3H), 2.05-2.01 (m, 2H), 1.45-1.40 (m, 2H), 1.15-1.10 (m, 2H); m/z (ES)⁺: 381 [M+H]⁺.

b) 3-{2-Aminopyridin-5yl)-N-(4-morpholino-trans-cyclohexyl)imidazo[1,2-b]pyridazin- 6-amine

N

NH₂

A mixture of 3-bromo-/\/-(4-morpholino-trans-cyclohexyl)imidazo[1 ,2-b]pyridazin-6-amine (1.30 g, 3.42 mmol, 1.0 eq), 2-aminopyrimidine-5-boronic acid pinacol ester (1.13 g, 5.11 mmol, 1.5 eq), Na₂C0₃ (1.09 g, 10.28 mmol, 3.0 eq) in DMF (25 ml_) and water (10 mL) was degassed using argon for 30 min. To the mixture, Pd(dppf)CI₂ (250mg, 0.34 mmol, 10 mol %) was added and further degassed for 30 min. The reaction mixture was heated at 100°C for 1 h. The reaction mixture was cooled to RT, H₂0 added (150 mL) and the precipitated solid collected by filtration, washed with EtOAc and dried to give an off-white solid (950 mg, 70%); ¹H NMR (400MHz, DMSO- /₆) δ ppm 8.98 (s, 2H), 7.79 (s, 1H), 7.70 (d, J=10.0 Hz, 1 H), 6.97 (d, J=6.8 Hz, 1 H), 6.86 (s, 2H), 6.62 (d, J=10.0 Hz, 1 H), 3.57-3.49 (m, 4H), 2.50-2.40 (m, 4H), 2.30-2.10 (m, 4H), 2.00-1.90 (m, 2H), 1.40-1.20 (m, 4H); m/z (APCI)⁺: 395 [M+H]⁺.

c) 3-(2-(3-Fluoropyridin-2-yIamino)pyrimidin-5-yI)-N-(4-morphoIino-trans- cyclohexyl)imidazo[1,2-b] ridazin-6-amine

A mixture of 3-(2-Aminopyridin-5yl)-N-(4-morpholino-irans-cyclohexyl)imidazo[1 ,2- b]pyridazin-6-amine (150 mg, 0.38 mmol, 1.0 eq), 2-chloro-3-fluoropyridine (100 mg, 0.76 mmol, 2.0 eq), Xantphos (22 mg, 0.04 mmol, 0.1 eq) and Cs₂C0₃ (496 mg, 1.52 mmol, 4.0 eq) in 1 ,4-dioxane (8 mL) was degassed using argon for 45 min. Pd(PPh₃)₄ (44 mg, 0.04 mmol, 0.1 eq) was added and the mixture further degassed for 45 min. The reaction mixture was heated at 130°C in a sealed tube for 6 h, then cooled to RT, H₂0 added (30 mL) and extracted with 20% MeOH/CHCI₃ (2 x 20mL). The combined organic extracts were washed with brine solution (20 mL), dried (Na₂S0₄) and concentrated. The crude compound was purified by neutral alumina chromatography (2% MeOH/CHCI₃) to give a pale yellow solid (120 mg, 64%); ¹H NMR (400MHz, DMSO-cf₆) δ ppm 10.02 (s, 1 H), 9.16 (s, 2H), 8.22 (d, J=4.4 Hz ,1 H), 7.88 (s, 1 H), 7.67-7.73 (m, 2H), 7.31-7.27 (m, 1 H), 7.06- 7.04 (m, 1 H), 6.66 (d, J=10.0 Hz, H), 3.72-3.40 (m, 5H), 2.50-2.40 (m, 4H), 2.30-2.10 (m, 3H), 2.01-1.80 (m, 2H), 1.40-1.20 (m, 4H); m/z (ES)⁺: 490 [M+H]⁺.

Intermediate 5

A mixture of intermediate 1 (1.00 g, 2.44 mmol, 1.0 eq), 2-amino-3-fluoropyridine-5-boronic acid pinacol ester (700 mg, 2.92 mmol, 1.2 eq), Cs₂C0₃ (3.18 g, 9.75 mmol, 4.0 eq), water (2 mL) and THF (15 mL) was degassed with N₂, then Pd(dppf)CI₂ (100 mg, 0.12 mmol, 0.05 eq) was added and the mixture heated at 80°C for 2 h. Purification by column chromatography on silica gel (2-20% MeOH/DCM) gave an off-white solid (780 mg, 72%); ¹H NMR (400 MHz, DMSO-d₆) δ ppm 8.59 (s, 1 H), 8.16 (dd, .7=1.8, 13.3 Hz, 1 H), 7.80 (s, 1 H), 7.70 (d, J=9.6 Hz, 1 H), 6.97 (d, J=6.9 Hz, 1 H), 6.85 (d, J=7.8 Hz, 1 H), 6.62 (d, J=9.6 Hz, 1 H), 6.40 (s, 2H), 3.40-3.56 (m, 1H), 3.19-3.30 (m, 1 H), 2.06-2.25 (m, 2H), 1.78-1.97 (m, 2H), 1.39 (s, 9H), 1.15-1.34 (m, 4H); m/z (ES+APCI)⁺: 442 [M+Hf.

Example 53

frans-A/-{3-[5-Fluoro-6-(pyridin-2-ylamino)pyridin-3-yI]imidazo[1 ,2-fa]pyridazin-6- yl}cyc!ohexane-1 ,4-diam ine

Following the method for example 16 using 2-chloropyridine gave a yellow solid (70 mg, 28%); ¹H NMR (400 MHz, DMSO-d₆) δ ppm 9.28 (s, 1H), 8.88 (d, J=1.4 Hz, 1 H), 8.51 (dd, J=2.1 , 13.1 Hz, 1 H), 8.29-8.19 (m, 1H), 7.99 (s, 1 H), 7.91 (d, J=8.7 Hz, 1 H), 7.76 (d, J=9.6 Hz, 1 H), 7.72 (ddd, J=2A , 7.1 , 8.7 Hz, 1 H), 7.06 (d, J=6.9 Hz, 1 H), 6.95 (ddd, J=1.1 , 4.9, 7.2 Hz, 1 H), 6.69 (d, J=10.1 Hz, 1 H), 3.52 (br. s, 1 H), 2.75-2.62 (m, 1H), 2.24-2.10 (m, 2H), 1.95-1.79 (m, 2H), 1.41-1.12 (m, 4H); m/z (ES+APCI)⁺: 419 [M+H]⁺.

Example 54

a) 3-Bromo-N-4-(pyrrolidin-1- I)-trans-cycIohexyl)imidazo[1,2-b]pyridazin-6-amine

To a solution of /V-1-(3-bromoimidazo[1 ,2-b]pyridazin-6-yl)-trans-cyclohexane-1 ,4-diamine (500 mg, 1.61 mmol 1.0 eq) and 1 ,4-dibromobutane (291 μΙ_, 524 mg, 1.5 eq) in anhydrous D F (4 ml_) was added K₂C0₃ (670 mg, 4.85 mmol, 3.0 eq) and the reaction mixture was heated at 70^°C for 4 h. The reaction mixture Was cooled to RT, concentrated and purification by neutral alumina chromatography (10% MeOH/CHCI₃) gave an off-white solid (150 mg, 25%); ¹H NMR (400MHz, CDCI₃) δ ppm 7.58 (d, J=9.6 Hz, 1 H), 7.47 (s, 1 H), 6.41 (d, J=10.0 Hz, 1 H), 4.29 (d, J=6.8 Hz, 1 H), 3.77-3.71 (m, 1 H), 2.62 (s, 4H), 2.27-2.24 (m, 2H), 2.12-2.08 (m, 3H), 1.8 (s, 4H), 1.52-1.46 (m, 2H), 1.29-1.23 (m, 2H); m/z (APCI)⁺: 364 [M+H]⁺.

b) 3-(2-Aminopyrimidin-5-yl)-N-(4-(pyrrolidin-1-yl)-trans-cyclohexyl)imidazo[1,2- b]pyridazin-6-amine

A mixture of 3-bromo-N-(4-(pyrrolidin-1-yl)-trans-cyclohexyl)imidazo[1,2-b]pyridazin-6- amine (150 mg, 0.41 mmol, 1.0 eq), 2-aminopyrimidine-5-boronic acid pinacol ester (136 mg, 0.61 mmol, 1.5 eq), Na₂C0₃ (175 mg, 1.65 mmol, 4.0 eq) in DMF (5 mL) and water (1 mL) was degassed using argon for 30 min. To the mixture (Aphos)₂PdCI₂ (30 mg, 5 mol %) was added and further degassed for 30 min. The reaction mixture was heated at 100°C for 4 h. The reaction mixture was cooled to RT, concentrated and purified by neutral alumina chromatography (10-40% MeOH/CHCI₃) to give an off-white solid (100 mg, 64%); ¹H NMR (400MHz, DMSO-d₆) δ ppm 8.99 (s, 2H), 7.8 (s, 1 H), 6.99 (d, J=3.2 Hz, 1 H), 6.86 (s, 2H), 6.71 (s, 1 H), 6.62 (d, J=9.6 Hz, 1 H), 3.54 (s, 1 H), 2.11-2.01 (m, 5H), 1.67 (s, 4H), 1.33- 1.23 (m, 4H), 1.06 (s, 4H); m/z (APCI)⁺: 379 [M+H]⁺.

c) 3-(2-(3-Fluoropyridin-2-ylamino)pyrimidin-5-yl)-N-(4-(pyrroIidin-1-yI)-trans- cyclohexyl) imidazo [1,2-b pyri dazin-6-am i ne

A mixture of 3-(2-aminopyrimidin-5-yl)-N-(4-(pyrrolidin-1-yl)-trans-cyclohexyl)imidazo [1 ,2- b]pyridazin-6-amine (100 mg, 0,26 mmol, 1.0 eq), 2-chloro-3-fluoropyridine (52 μΙ_, 69 mg, 0.52 mmol, 2.0 eq), Xantphos (15 mg, 0.02 mmol, 0.1 eq) and Cs₂C0₃ (338 mg, 1.04 mmol, 4.0 eq) in 1 ,4-dioxane (5 mL) was degassed using argon for 30min. Pd(PPh₃)₄ (30 mg,0.02 mmol, 0.1 eq) was then added and the mixture further degassed for 5 min. The reaction mixture was heated at 30°C in a sealed tube for 6 h, then cooled to RT, concentrated and purified by prep-HPLC to give an off-white solid (50 mg, 40%); H NMR (400MHz, CDCI₃) δ ppm 12.45 (s, 1 H), 9.14 (s, 2H), 8.29 (d, J=5.2 Hz, 1 H), 7.77-7.70 (m, 2H), 7.49-7.46 (m, 1 H), 7.08-7.03 (m, 1 H), 6.48 (d, J=10.4 Hz, 1 H), 4.40 (d, J=6.8 Hz, 1 H), 3.72 (m, 2H), 3.08- 2.91 (m, 3H), 2.42-2.26 (m, 6H), 2.01-1.85 (m, 4H), 1.43-1.31 (m, 3H); m/z (ES)⁺: 474 [M+H]⁺.

Example 55

5-[6-(2,5-DiazabicycIo[2.2.1]hept-2-yl)imidazo[1,2^]pyridazin-3-yl3-N-(3-fIuoropyridin- 2-yl)pyrimidin-2-amine

a) iert-Butyl 5-(3-bromoimidazo[1 ,2-b]pyridazin-6-yI)-2,5diazabicyclo[2.2.1]heptane-2- carboxylate

3-Bromo-6-chloroimidazo[1 ,2-b]pyridazine (586 mg, 2.53 mmol) was dissolved in NMP (5 mL) and 2,5-diazabicyclo[2.2.1]heptane-2-carboxylic acid 1 ,1-dimethylethyl ester (1.0 g, 5.05 mmol) was added followed by DIPEA (1.04 mL, 6.31 mmol). The reaction mixture was heated to 30°C for 4 h. The solution was cooled down and diluted with DCM, then washed twice with water and twice with brine. The solution was dried over magnesium sulphate and solvents evaporated. Purification by column chromatography on silica gel (10- 00% EtOAc/petroleum ether) gave a brown oil. This was dissolved in ethyl acetate, washed four more times with brine, dried over magnesium sulphate and the solvents evaporated to give a brown solid (486 mg, 49%); H NMR (400 MHz, CDCI₃) δ ppm 7.67 (d, J=9.6 Hz, 1 H), 7.67 (d, J=9.6 Hz, 1 H), 7.52 (s, 1 H), 6.54 (d, J=9.6 Hz, 1 H), 4.49-4.84 (m, 2H), 3.43-3.67 (m, 4H), 1.94-2.07 (m, 2H), 1.48 (s, 9H); m/z (ES+APCIf: 394/396 [M+H]⁺.

h) iert-Butyl 5-[3-(2-aminopyrimidin-5-yl)imidazo[1 , 2-b] py ri d azi n -6-y I] -2, 5- diazabicyclo[2.2.1]heptane-2-carboxylate

ferf-Butyl 5-(3-bromoimidazo[1 ,2-b]pyridazin-6-yl)-2,5-diazabicyclo[2.2.1]heptane-2- carboxylate (480 mg, 1.22 mmol), 2-aminopyrimidine-5-boronic acid pinacol ester (350 mg, 1.58 mmol), Cs₂C0₃ (1.59 mg, 4.87 mmol) and Pd(dppf)Cl_z (99 mg, 0.12 mmol) were combined in a solution of THF (5 ml.) and water (1 mL) and solvents degassed with N₂. The reaction mixture was heated to 80°C for 4 h. The solvents were evaporated and the crude mixture purified by column chromatography on silica gel (0-10% 2M ammonia in MeOH/DCM) to give a yellow solid (373 mg, 75%); ¹H NMR (400 MHz, DMSO-c/₆) δ ppm 8.95 (s, 2H), 7.84-7.92 (m, 1H), 7.46-7.59 (m, 1 H), 6.90-6.99 (m, 1 H), 6.85 (s, 2H), 4.79 (br. s, 1 H), 4.44-4.54 (m, 1 H), 3.60 (br. s, 1 H), 3.39-3.46 (m, 2 H), 3.28 (br. s, 1 H), 1.96 (d, J=10.1 Hz, 2H), 1.28-1.44 (m, 9H); m/z (ES+APCI)⁺: 409 [M+Hf.

c) f erf-Butyl 5-(3-{2-[(3-fluoropyridin-2-yl)amino]pyrimidin-5-yl}imidazo[1 ,2- b]pyridazin-6-yl)-2,5-diazabic clo[2.2.1]heptane-2-carboxylate

te/f-Butyl 5-[3-(2-aminopyrimidin-5-yl)imidazo[1 ,2-b]pyridazin-6-yl]-2,5-diazabicyclo

[2.2.1]heptane-2-carboxylate (362 mg, 0.88 mmol), 2-chloro-3-fluoropyridine (139 mg, 1.06 mmol), Cs₂C0₃ (1.73 mg, 5.30 mmol), Pd(OAc)_z (60 mg, 0.26 mmol) and Xantphos (153 mg, 0.26 mmol) were combined in dioxane (5 mL) and solvents degassed with N₂. The mixture was heated at reflux for 3 h, then it was cooled down and the solvents evaporated. The crude mixture was purified by column chromatography on silica gel (0-10% MeOH/DCM) to give a yellow solid (329 mg, 74%); ¹H NMR (400 MHz, DMSO-d₆) δ ppm 9.13 (s, 1 H), 8.20-8.30 (m, 1 H), 7.94 (s, 1H), 7.62-7.76 (m, 3H), 7.29-7.42 (m, 3H), 4.80 (br. s, H), 4.51 (br. s, 1 H), 3.62 (dd, J=10.1 , 1.8 Hz, 1 H), 3.36-3.48 (m, 2H), 3.28-3.30 (m, 1 H), 1.96 (s, 2H), 1.38 (s, 9H); m/z (ES+APCI)⁺: 504 [M+H]⁺.

d) 5-[6-(2,5-diazabicycIo[2.2.1]hept-2-yl)imidazo[1,2-b]pyridazin-3-yI3-N-(3- fluoropyridin-2-yl)pyrimidin-2-amine

4M HCI in dioxane (5 ml_) was added to ferf-butyl 5-(3-{2-[(3-fluoropyridin-2- yl)amino]pyrimidin-5-yl}imidazo[1 ,2-b]pyridazin-6-yl)-2,5-diazabicyclo[2.2.1]heptane-2- carboxylate (325 mg, 0.65 mmol) and the reaction mixture stirred at RT for 2 h. The solvents were evaporated and the crude material purified by prep-HPLC. The product was eluted through an lsolute-NH₂ cartridge (MeOH), to give a yellow solid (5 mg, 2%); 1H NMR (400 MHz, DMSO-de) δ ppm 10.00 (s, 1 H), 9.19 (s, 2H), 8.25 (dt, J=4.6, 1.4 Hz, 1 H), 7.98 (s, 1 H), 7.89 (d, J=9.6 Hz, 1 H), 7.76 (ddd, J=10.5, 8.2, 1.4 Hz, 1 H), 7.31 (ddd, J=8.1 , 4.7, 3.7 Hz, 1H), 6.95 (d, J=9.6 Hz, 1 H), 4.66 (s, 1 H), 3.68 (s, 1 H), 3.50-3.55 (m, 1 H), 3.29 (br. s, 1 H), 2.82-2.95 (m, 2H), 1.81 (d, J=9.2 Hz, 1 H), 1.71 (d, J=9.2 Hz, 1 H); m/z (ES+APCI)⁺: 404 [M+H]⁺.

Example 56

W-(3-fIuoropyridin-2-yl)-5-[6-(5-methyl-2,5-diazabicyclo[2.2.1]hept-2-yI)imidazo[1,2- b]pyridazin-3-yl]pyrimidin-2-amine

5-[6-(2,5-diazabicyclo[2.2.1]hept-2-yl)imi

yl)pyrimidin-2-amine (100 mg, 0.25 mmol) was dissolved in THF (1 mL) and formaldehyde (37% solution in water, 20 μΙ_, 0.25 mmol) was added followed by acetic acid (28 μί, 0.50 mmol), then sodium triacetoxyborohydride (106 mg, 0.50 mmol). The reaction mixture was stirred at RT under N₂ for 2 h. Methanol was added, followed by a 2 M aqueous sodium hydroxide solution, and the mixture stirred at room temperature for 10 min, then concentrated to dryness. Purification by prep-HPLC gave a yellow solid (7 mg, 7%); 1 H NMR (400 MHz, DMSO-d₆) δ ppm 9.98 (s, 1 H), 9.17 (s, 2H), 8.24 (dt, =4.6, 1.4 Hz, 1 H), 7.98 (s, 1 H), 7.89 (d, J=10.1 Hz, 1H), 7.75 (ddd, J=10.5, 8.2, 1.4 Hz, 1 H), 7.30 (ddd, J=8.1 , 4.7, 3.7 Hz, 1H), 6.95 (d, J=10.1 Hz, 1H), 4.61 (s, 1 H), 3.47-3.60 (m, 2H), 3.38 (dd, J=10.1 , 1.8 Hz, 1 H), 3.16 (d, J=5.0 Hz, 1 H), 2.87 (dd, J=9.2, 1.8 Hz, 1 H), 2.30 (s, 3H), 1.89-1.96 (m, 1 H), 1.80 (d, J=9.2 Hz, 1 H); m/z (ES+APCIf: 418 [M+Hf.

Example 57

3-{4-[(3-Fluoropyridin-2-yl)amino]phenyl}-/V-(piperidin-4-yl)imidazo[1,2- ]pyridazin-6- amine

a) f erf-Butyl 4-{[3-(4-aminophenyl)irnidazo[1,2-fa]pyridaz!n-6-yI]amino}piperidine-1- carboxylate

Following the method for Intermediate 5 using Intermediate 4a and 4-aminophenylboronic acid pinacol ester gave a yellow solid (171 mg, 84%); ¹H NMR (400 MHz, DMSO-cf₆) δ ppm 7.78-7.88 (m, 2H), 7.68 (d, J=9.6 Hz, 1 H), 7.63 (s, 1 H), 6.94 (d, J=6.4 Hz, 1 H), 6.60-6.67 (m, 2H), 6.58 (d, J=9.6 Hz, 1H), 5.27 (s, 2H), 3.85-4.01 (m, 2H), 3.70-3.85 (m, 1 H), 2.87- 3.05 (m, 2H), 2.00-2.13 (m, 2H), 1.27-1 ,48 (m, 11 H); m/z (ES+APCI)⁺: 409 [M+Hf.

b) 3-{4-[(3-Fluoropyridin-2-yl)amino]phenyl}-A/-(piperidin-4-yl)imidazo[1,2- b] py r i dazi n -6-am i n e

Following the method for example 16 using ferf-butyl 4-{[3-(4-aminophenyI)imidazo[1 ,2- b]pyridazin-6-yl]amino}piperidine-1-carboxylate and 2-chloro-3-fluoropyridine gave an off- white solid (8 mg, 25%); ¹H NMR (400 MHz, DMSO-d₆) δ ppm 8.97 (d, .7=1.8 Hz, 1 H), 8.06- 8.15 (m, J=8.7 Hz, 2H), 7.98-8.05 (m, 1 H), 7.84-7.92 (m, J=8.7 Hz, 2H), 7.80 (s, 1H), 7.72 (d, J=9.6 Hz, 1 H), 7.57 (ddd, J=1.4, 7.9, 11.8 Hz, 1 H), 6.96 (d, J=6.9 Hz, 1 H), 6.83 (ddd, J=3.2, 4.8, 8.0 Hz, 1 H), 6.65 (d, J=9.6 Hz, 1H), 3.62-3.79 (m, 1 H), 2.96-3.09 (m, 2H), 2.56- 2.66 (m, 2H), 1.98-2.12 (m, 2H), 1.25-1.44 (m, 2H); m/z (ES+APCI)⁺: 404 [M+H]⁺. Example 58

3-[1 -(3-fluoropyridin-2-yi)-1 W-pyrazoI-4-yl]-W-(piperidin-4-yI)imidazo[1 ,2-b]pyridazin- 6-amine

a) 3-f Iuoro-2-(1 H-pyrazol-1 -yl)pyridine

A microwave vessel was charged with pyrazole (202 mg, 2.97 mmol, 1.0 eq), copper (I) iodide (113 mg, 0.59 mmol, 0.2 eq), L-Proline (137 mg, 1.19 mmol, 0.4 eq), 2-bromo-3- fluoropyridine (628 mg, 3.57 mmol, 1.2 eq) and K₂C0₃ (1.23 g, 8.90 mmol, 3.0 eq). It was then evacuated and back-filled with nitrogen (3 cycles). Anhydrous DMSO (3 mL) was added and the mixture stirred at 90^°C for 72 h. The reaction was then diluted with water (30 mL) and extracted with EtOAc (5 x 15 mL). The combined organic extracts were washed with water (2 x 50 mL), dried (MgS0₄) and concentrated in vacuo. Chromatography on silica gel (12-100% EtOAc in petrol) afforded a clear liquid (256 mg, 53%); ¹H NMR (400 MHz, DMSO-cfe) δ ppm 8.44-8.43 (m, 1H), 8.38 (dt, J=4.6, 1.1 Hz, 1 H), 8.05-7.98 (m, 1H), 7.86-7.85 (m, 1 H), 7.55-7.50 (m, 1 H), 6.60 (dd, J=2.7, 1.8 Hz, 1 H); m/z (ES+APCI)⁺: 164 [M+H]⁺.

b) 2-(4-Bromo-1 W-pyrazoI-1 -yl)-3-fluoropyridine

A solution of 3-fluoro-2-(1 H-pyrazol-1-yl)pyridine (282 mg, 1.73 mmol) in glacial acetic acid (3 mL) was treated dropwise with a solution of bromine (0.26 mL, 5.18 mmol, 3.0 eq) in acetic acid (1 mL) and stirred at room temperature for 1 h. The reaction was then quenched with saturated aqueous sodium metabisulfite until the colour of bromine had disappeared, and then extracted with EtOAc (3 x 10 mL). The organic extracts were washed with water (2 x 30 mL), dried (MgS0₄), concentrated in vacuo and purified by chromatography on silica gel (5-35% EtOAc/petroleum ether) to give a white solid (361 mg, 86%); ¹H NMR (400 MHz, DMSO-d₆) δ ppm 8.66 (s, 1 H), 8.39 (dt, J=4.6, 1.1 Hz, 1H), 8.08- 8.02 (m, 1H), 7.99 (s, 1H), 7.61-7.54 (m, 1 H); m/z (ES+APCIf: 242/244 [M+H]⁺.

c) 3-Fluoro-2-[4-(4,4,5,5-tetrameth l-1 ,3,2-dioxaborolan-2-yl)-1 H-pyrazol-1 -yl]pyridine

A microwave vial was charged with 2-(4-bromo-1/-/-pyrazol-1-yl)-3-fluoropyridine (300 mg, 1.24 mmol), bis-pinacolatodiboron (787 mg, 3.10 mmol, 2.5 eq), PdCI₂(dppf) (101 mg, 0.12 mmol, 0.1 eq) and KOAc (486 mg, 4.96 mmol, 4.0 eq). Degassed dioxane (3.5 mL) was added and the tube sealed and stirred at 100°C for 18 h. It was then diluted with EtOAc (10 mL), filtered through a pad of celite, concentrated in vacuo and chromatographed on silica gel (5-40% EtOAc/petroleum ether) to give a pale yellow oil (163 mg, 45%); H NMR (400 MHz, DMSO-d₆) δ ppm 8.53 (s, 1 H), 8.39 (dt, J=4.6, 1.0 Hz, 1 H), 8.04 (ddd, J=11.0, 8.2, 1.4 Hz, 1H), 7.95 (s, 1H), 7.59-7.54 (m, 1 H), 1.30 (s, 12H); m/z (ES+APCI)⁺: 290 [M+H]⁺. d) ferf-Butyl 4-({3-[1-(3-fluoropyridin-2-yI)-1 W-pyrazol-4-yl]imfdazo[1 ,2- ]pyridazin-6- yl}amino)piperidine-1 -c

A microwave vial was charged with intermediate 1 (80 mg, 0.20 mmol), PdCI₂(dppf) (33 mg, 0.040 mmol, 0.2 eq), 3-fluoro-2-[4-(4,4,5,5-tetramethyl-1 ,3,2-dioxaborolan-2-yl)-1 H-pyrazol- 1-yl]pyridine (2.5 eq, 0.50 mmol, 146 mg) and Cs₂C0₃ (263 mg, 0.81 mmol, 4.0 eq). Degassed dioxane (0.5 mL) was added and the tube sealed and stirred at 00°C for 18 h. Concentration in vacuo directly onto silica and chromatography on silica gel (0-10% 2 NH₃/MeOH in CH₂CI₂) gave a pale brown solid (18 mg, 18%); ¹H NMR (400 MHz, DMSO- d₆) δ ppm 9.23 (s, 1 H), 8.50 (s, 1 H), 8.34-8.32 (m, 1 H), 8.04 (ddd, J=11.4, 8.2, 1.4 Hz, 1 H), 7.91 (s, 1 H), 7.77 (d, J=9.6 Hz, 1 H), 7.56-7.52 (m, 1 H), 7.15 (d, J=6.4 Hz, 1 H), 6.67 (d, J=9.6 Hz, 1 H), 4.00-3.87 (m, 3H), 3.20 (s, br, 2H), 2.17-2.13 (m, 2H), 1.43 (s, 9H) 1.42- 1.35 (m, 2H); m/z (ES+APCI)⁺ : 479 [M+H]⁺.

e) 3-[1-(3-Fluoropyridin-2-yl)-1H-pyrazol-4-yl]- V-(piperidin-4-yI)imidazo[1,2- ]pyridazin-6-amine

A solution of ferf-butyl 4-({3-[1-(3-fluoropyridin-2-yl)-1H-pyrazol-4-yl]imidazo[1 ,2- fc>]pyridazin-6-yl}amino)piperidine-1 -carboxylate (16 mg, 0.033 mmol) in MeOH (2 mL) was treated with 4M HCI in dioxane (2 mL) and stirred at room temperature for 2 h. It was then basified with 2M NH₃ in MeOH, concentrated in vacuo and the residue purified by prep- HPLC to give an off-white solid (7 mg, 56%); Ή NMR (400 MHz, DMSO-d₆) δ ppm 9.25 (s, 1 H), 8.50 (s, 1 H), 8.39 (d, J=4.6 Hz, 1 H), 8.04 (ddd, J=11.9, 8.2, 1.4 Hz, 1 H), 7.89 (s, 1H), 7.75 (d, J=9.6 Hz, 1H), 7.54 (ddd, J=8.5, 4.7, 3.2 Hz, 1 H), 7.11 (br. d, J=6.4 Hz, 1 H), 6.67 (d, J=9.6 Hz, 1 H), 3.85-3.75 (m, 1 H), 3.06 (br. d, J=12.8 Hz, 2H), 2.73 (br. t, J=11.2 Hz, 2H), 2.11 (br. d, J=10.5 Hz, 2H), 1.40 (br. qd, J=11.7, 3.4 Hz, 2H); m/z (ES+APCI)⁺: 378 [M+H]⁺.

Example 59

3-{6-[(3-Fluoropyridin-2-yl)amino]pyridin-3-yI}-A/-(1-methylpiperidin-4-yI)imidazo[1,2- J ]pyridazin-6-amine

a) fert-Butyl 4-{[3-(6-aminopyridin-3-yl)imidazo[1 ,2-b]pyridazin-6-yi]amino}piperidine- 1 -carboxylate

Following the method for fert-butyl (frans-4-{[3-(6-amino-5-fluoropyridin-3-yl)imidazo[1 ,2- b]pyridazin-6-yl]amino}cyclohexyl)carbamate using Intermediate 4a and 2-aminopyridine-5- boronic acid pinacol ester gave an off-white solid (312 mg, 91 %); H NMR (400 MHz, DMSO-d₆) δ ppm 8.69 (d, J=1.8 Hz, 1 H), 8.07 (dd, J=2.3, 8.7 Hz, 1 H), 7.65-7.74 (m, 2H), 7.00 (d, .7=6.4 Hz, 1 H), 6.61 (d, J=10.1 Hz, 1H), 6.54 (dd, J=0.9, 8.7 Hz, 1 H), 6.12 (s, 2H), 3.83-3.96 (m, 2H), 3.68-3.82 (m, 1 H), 2.84-3.04 (m, 2H), 1.96-2.11 (m, 2H), 1.27-1.47 (m, 11 H); m/z (ES+APCIf: 410 [M+H]⁺.

b) 3-{6-[(3-Fluoropyridin-2-yI)amino]pyridin-3-yl}-W-(piperidin-4-yl)imidazo[1,2- b]pyridazin-6-amine

Following the method for example 16 using ferf-butyl 4-{[3-(6-aminopyridin-3- yl)imidazo[1 ,2-6]pyridazin-6-yl]amino}piperidine-1-carboxylate and 2-chloro-3- fluoropyridine gave an off-white solid (32 mg, 33%); ¹H NMR (400 MHz, DMSO-d₆) δ ppm 9.30 (br. s, 1H), 9.01-9.13 (m, 1H), 8.42 (dd, J=2.5, 8.9 Hz, 1 H), 8.09-8.19 (m, 1H), 8.04- 8.09 (m, 1 H), 7.87 (s, 1H), 7.74 (d, J=9.6 Hz, 1H), 7.65 (ddd, J=1.4, 8.0, 11.2 Hz, 1H), 6.94-7.09 (m, 2H), 6.68 (d, J=10.1 Hz, 1 H), 3.59-3.77 (m, 1H), 2.89-3.06 (m, 2H), 2.52-2.63 (m, 2H), 1.87-2.07 (m, 2H), 1.20-1.43 (m, 2H); m/z (ES+APCI)⁺: 405 [M+H]⁺.

c) 3-{6-[(3-Fluoropyridin-2-yl)amino]pyridin-3-yl}-/V-(1-methylpiperidin-4- yl)imidazo[1,2-b]pyridazin-6-amine

Following the method for example 27 using 3-{6-[(3-fluoropyridin-2-yl)amino]pyridin-3-yl}-A/- (piperidin-4-yl)imidazo[1,2-b]pyridazin-6-amine gave a yellow solid (22 mg, 76%); ¹H NMR (400 MHz, DMSO-d_s) δ ppm 9.31 (s, 1H), 9.07 (d, J=2.3 Hz, 1H), 8.36-8.45 (m, 1H), 8.09- 8.15 (m, 1 H), 8.06 (d, J=8.2 Hz, 1H), 7.87 (s, 1H), 7.75 (d, J=9.6 Hz, 1H), 7.65 (ddd, J=1.4, 8.0, 11.2 Hz, 1 H), 6.94-7.07 (m, 2H), 6.69 (d, J=9.6 Hz, 1H), 3.60 (d, J=6.4 Hz, 1 H), 2.70- 2.81 (m, 2H), 2.19 (s, 3H), 1.97-2.12 (m, 4H), 1.38-1.60 (m, 2H); m/z (ES+APCI)⁺: 419 [M+H]⁺

Example 60

3-{4-[(3-fluoropyridin-2-yl)amino]phenyl}-^-(1-methylpiperidin-4-yl)imidazo[1,2- fo]pyridazin-6-amine

Following the method for example 27 using 3-{4-[(3-fluoropyridin-2-yl)amino]phenyl}-/\/- (piperidin-4-yl)imidazo[1 ,2-b]pyridazin-6-amine gave a yellow solid (5 mg, 70%); ¹H NMR (400 MHz, DMSO-d₆) δ ppm 9.00 (d, J=1.8 Hz, 1 H), 8.06-8.14 (m, 2H), 7.97-8.04 (m, 1 H), 7.85-7.94 (m, 2H), 7.80 (s, 1 H), 7.72 (d, J=9.6 Hz, 1 H), 7.51-7.62 (m, 1 H), 6.97 (d, J=6.4 Hz, 1 H), 6.84 (ddd, J=3.4, 4.7, 7.9 Hz, 1 H), 6.65 (d, J=9.6 Hz, 1 H), 3.47-3.68 (m, 1 H), 2.74-2.89 (m, 2H), 2.20 (s, 3H), 1.99-2.12 (m, 4H), 1.42-1.60 (m, 2H); m/z (ES+APCIf: 418 [M+Hf. Example 61

3-[3-FIuoro-4-(pyridin-2-yIamino)phenyl]-W-(piperidin-4-yl)imidazo[1,2-ft]pyridazin amine

a) ierf-Butyl 4-{[3-(4-amino-3-fluorophenyl)imidazo[1,2-/ ]pyridazin-6- yl]amino}piperidine-1 -carboxylate

Following the method for Intermediate 5 using Intermediate 4a and 4-amino-3- fluorophenylboronic acid pinacol ester gave an off-white solid (250 mg, 56%); H NMR (400 MHz, DMSO-d₆) δ ppm 7.98 (dd, J=2.1 , 14.0 Hz, 1 H), 7.78 (s, 1 H), 7.73 (d, J=9.6 Hz, H),- 7.64 (dd, J=1.8, 8.2 Hz, 1 H), 7.08 (d, J=6.4 Hz, 1 H), 6.83 (dd, J=8.2, 9.6 Hz, 1 H), 6.64 (d, J=9.6 Hz, 1H), 5.35 (br. s, 2H), 3.88-4.04 (m, 2H), 3.69-3.84 (m, 1H), 2.85-3.05 (m, 2H),

2.04-2.14 (m, 2H), 1.28-1.45 (m, 11 H); m/z (ES+APCI)⁺: 427 [M+H]⁺.

b) 3 3-Fluoro-4-(pyridin-2-ylamino)phenyl]-W-(piperidin-4-yl)imidazo[1,2-fa]pyri

6-amine

Following the method for example 16 using terf-butyl 4-{[3-(4-amino-3- fluorophenyl)imidazo[1 ,2-i ]pyridazin-6-yl]amino}piperidine-1-carboxylate and 2- chloropyridine gave a yellow solid (17 mg, 28%); ¹H NMR (400 MHz, DMSO-d₆) δ 8.75- 8.89 (m, 1H), 8.25-8.36 (m, 2H), 8.16 (dd, =1.4, 5.0 Hz, 1H), 7.90 (s, 1H), 7.84 (dd, J=1.8, 8.7 Hz, 1H), 7.74 (d, J=10.1 Hz, 1H), 7.59 (ddd, J=1.8, 7.0, 8.6 Hz, 1H), 6.98-7.08 (m, 2H), 6.79 (ddd, J=0.9, 5.5, 6.4 Hz, 1 H), 6.67 (d, J=9.6 Hz, 1 H), 3.62-3.77 (m, 1H), 2.94-3.08 (m, 2H), 2.54-2.65 (m, 2H), 1.97-2.16 (m, 2H), 1.25-1.42 (m, 2H); m/z (ES+APCI)⁺: 404 [M+H]⁺.

Example 62

3-[3-fluoro-4-(pyridin-2-ylamino)phenyl]- V-(1 -methylpiperidin-4-yl)imidazo[1 ,2- b] py ri d azi n -6-am i n e

Following the method for example 27 using 3-[3-fluoro-4-(pyridin-2-ylamino)phenyl]-N- (piperidin-4-yl)imidazo[1 ,2-fc]pyridazin-6-amine gave a yellow solid (7 mg, 62%); ¹H NMR (400 MHz, DMSO-oy δ ppm 8.84 (s, 1 H), 8.27-8.39 (m, 2H), 8.16 (td, J=1.4, 5.0 Hz, 1 H), 7.91 (s, 1 H), 7.82 (dd, J=1.8, 8.7 Hz, 1 H), 7.75 (d, .7=9.6 Hz, 1 H), 7.54-7.63 (m, 1 H), 6.99- 7.11 (m, 2H), 6.79 (ddd, J=0.9, 5.5, 6.4 Hz, 1H), 6.68 (d, J=9.6 Hz, 1 H), 3.51-3.70 (m, 1 H), 2.75-2.89 (m, 2H), 2.19 (s, 3H), 1.99-2.16 (m, 4H), 1.40-1.60 (m, 2H); m/z (ES+APCI)⁺: 418 [M+Hf.

Example 63

^-(3-Fluoropyridin-2-yl)-5-[6-(piperidin-4-ylmethyl)imidazo[1,2-6]pyridazin-3- yl]pyrlmidin-2-amine

a) ferf-Butyl 4-(imidazo[1 ,2 ine-1 -carboxylate

To a solution of 1-Boc-4-methylene-piperidine (1.29 g, 6.5 mmol, 2.0 eq) in dry THF (10 mL) under nitrogen was added 9-BBN (0.5M in THF, 16.3 mL, 8.16 mmol, 2.5 eq). The reaction mixture was heated at 75°C for 3 h. After cooling, the resulting solution was added to a mixture of 6-chloroimidazo[1 ,2-b]pyridazine (0.5 g, 3.2 mmol), Pd(dppf)CI₂ (133 mg, 0.16 mmol, 0.05 eq) and K₂C0₃ (1.35 g, 9.8 mmol, 3.0 eq) in DMF (5 mL) and water (1 mL). The reaction mixture was heated at 75°C for 16 h then concentrated in vacuo. The residue was dissolved in EtOAc and washed with water (50 mL) and brine (20 mL). The organics were dried over MgS0₄ and concentrated in vacuo. Purification by chromatography on silica gel gave a solid (0.406 g, 40%); ¹H NMR (400 MHz, DMSO-d₆) δ ppm 8.21 (s, 1 H), 8.03 (d, J=9.1 Hz, 1 H), 7.71 (s, 1 H), 7.16 (d, J=9.1 Hz, 1 H), 3.91 (m, 2H), 2.55-2.79 (m, 4H), 1.92 (m, 1 H), 1.52-1.65 (m, 2H), 1.38 (s, 9H), 0.99-1.22 (m, 2H); m/z (ES+APCI)⁺: 317 [M+H]⁺.

b) fert-Butyl 4-[(3-bromoimi yl]piperidine-1 -carboxylate

To a solution of fe/f-butyl 4-(imidazo[1 ,2-b]pyridazin-6-ylmethyl)piperidine-1 -carboxylate (0.40 g, 1.26 mmol) in dry DCM (6 mL) was added dropwise a solution of NBS (0.246 g, 1.39 mmol, 1.1 eq) in dry acetonitrile (6 mL). The reaction mixture was stirred at room temperature for 1 hour. NBS (24 mg, 0.13 mmol) was added and the reaction mixture was stirred for a further hour. The reaction mixture was concentrated in vacuo. The residue was dissolved in DCM (100 mL) and washed with water (2 x 30 mL). The organics were dried over MgS0₄ and concentrated in vacuo. Purification by chromatography on silica gel gave a solid (0.42 g, 83%); ¹H NMR (400 MHz, DMSO-d₆) δ ppm 8.09 (d, J=9.1 Hz, H), 7.86 (s, 1 H), 7.26 (d, J=9.1 Hz, 1 H), 3.82-3.96 (m, 2H), 2.80 (d, J=6.87 Hz, 2H), 2.59-2.77 (m, 2H), 1.87-1.98 (m, 1 H), 1.55-1.64 (m, 2H), 1.38 (s, 9H), 1.01-1.24 (m, 2H).

c) feri-Butyl 4-{[3-(2-aminopyrimidin-5-yl)imidazo[1,2- 3]pyridazin-6- yl]methyl}piperidine-1-carboxylate

A mixture of terf-butyl 4-[(3-bromoimidazo[1 ,2-t)]pyridazin-6-yl)methyl]piperidine-1- carboxylate (0.289 g, 0.73 mmol), 2-aminopyridine-5-boronic acid (0.242 g, 1.09 mmol, 1.5 eq), Pd(dppf)Cl_z (30 mg, 0.036 mmol, 0.05 eq), and Cs₂C0₃ (0.953 g in 2 mL of water, 4.0 eq) in dioxane (10 mL) was heated at 95°C for 16 h. The reaction mixture was diluted with EtOAc (50 mL) and filtered, and the inorganic salts were washed with EtOAc. The filtrate was concentrated in vacuo then purification by chromatography on silica gel (0 to 10% MeOH in EtOAc) gave a yellow solid (0.170 g, 70%); H NMR (400 MHz, DMSO-cfe) δ ppm 8.93 (s, 2H), 8.10 (s, 1 H), 8.09 (d, J= 9.1 Hz, 1 H) 7.18 (d, J=9.1 Hz, 1 H), 6.93 (br. s, 2H), 3.85-395 (m, 2H), 2.79 (d, J=7.3 Hz, 2H), 2.75-2.55 (m, 2H), 1.89-2.03 (m, 1H), 1.58-1.70 (m, 2H), 1.38 (s, 9H), 1.03-1.21 (m, 2H); m/z (ES+APCI)⁺: 410 [M+H]⁺.

d) tert-Butyl 4-[(3-{2-[(3-fluoropyridin-2-yl)amino]pyrimidin-5-yl}imidazot1 ,2- b]pyridazin-6-y!)methyI]piperidine-1 -carboxylate

A mixture of te/f-butyl 4-{[3-(2-aminopyrimidin-5-yl)imidazo[1 ,2-£>]pyridazin-6- yl]methyl}piperidine-1-carboxylate (0.170 g, 0.4 mmol), 2-chloro-3-fluoropyridine (123 μΙ_, 1.24 mmol), Pd(OAc)₂ (27 mg, 0.12 mmol), xantphos (72 mg, 0.12 mmol), and Cs₂C0₃ (0.541 g, 1.66 mmol) in dioxane (5 mL) was heated at 120^DC under N₂. The reaction mixture was diluted with EtOAc/MeOH (8:2) and filtered. The inorganic salts were washed with EtOAc/MeOH (8:2). The filtrate was concentrated in vacuo. Purification by chromatography (0 to 10% MeOH in EtOAc) gave a yellow solid (0.101 g, 48%); ¹H NMR (400 MHz, MeOD-d₄) δ ppm 9.21 (s, 2H). 8.20-8.24 (m, H), 8.12 (s, 1 H), 8.01 (d, J=9.6 Hz, 1 H), 7.67 (ddd, J=10.2, 8.4, 1.6 Hz, 1 H), 7.18-7.31 (m, 2H), 4.01-4.13 (m, 2H), 2.87 (d, J=7.3 Hz, 2H), 2.65-2.85 (m, 2H), 2.05-2.15 (m, 1H), 1.65-1.80 (m, 2H), 1.44 (s, 9H), 1.15- 1.32 (m, 2H); m/z (ES+APCI)⁺: 505 [M+H]⁺.

e) W-(3-Fluoropyridin-2-yl)-5-[6-(piperidin-4-yImethyl)imidazo[1,2--b]pyridazin-3- yl]pyrimidin-2-amine

To a solution of feri-butyl 4-[(3-{2-[(3-fluoropyridin-2-yl)amino]pyrimidin-5-yl}imidazo[1 ,2- b]pyridazin-6-yl)methyl]piperidine-1-carboxylate (0.10 g, 0.19 mmol) in MeOH (2 mL) was added 4M HCI (2 mL) and the reaction mixture was stirred at room temperature for 2 h. The reaction mixture was concentrated in vacuo. The residue was purified by prep-LCMS to give the product as a TFA salt. The product was eluted through an Isolute aminopropyl cartridge to give a solid (75 mg, 94%); ¹H NMR (400 MHz, MeOD-d₄) δ ppm 9.20 (s, 2H), 8.19-8.24 (m, 1 H), 8.12 (s, 1 H), 8.01 (d, J=9.1 Hz, 1 H), 7.67 (ddd, J=10.5, 8.2, 1.3 Hz, 1 H), 7.21-7.31 (m, 2H), 3.04-3.13 (m, 2H), 2.88 (d, J=7.3 Hz, 2H), 2.67 (td, J=12.5, 2.7 Hz, 2H), 2.07-2.30 (m, 1H), 1.77 (m, 2H), 1.34 (qd, J=12.5, 4.1 Hz, 2H); A77/Z(ES+APCI)⁺: 405 [M+Hf.

Example 64

W-(3-Fluoropyridin-2-yl)-5-{6-[(1-methylpiperi

3-yl}pyrimidin-2-amine

A mixture of /V-(3-fluoropyridin-2-yl)-5-[6-(piperidin-4-ylmethyl)imidazo[1 ,2-6]pyridazin-3- yl]pyrimidin-2-amine (50 mg, 012 mmol), formaldehyde (11 μΙ_, 0.14 mmol), acetic acid (14 μΙ_, 0.24 mmol) and sodium triacetoxyborohydride (52 mg, 0.24 mmol) in dry THF (2 mL) and dry MeOH (0.1 mL) was stirred at room temperature for 30 mins. The reaction mixture was concentrated in vacuo and purification by chromatography on silica gel (0-30% MeOH in EtOAc containing ammonia) gave a yellow solid (34 mg, 65%); ¹H NMR (400 MHz, MeOD-cM δ ppm 9.16 (s, 2H), 8.17-8.25 (m, 1 H), 8.10 (s, 1 H), 8.01 (d, J=9.1 Hz, 1 H), 7.66 (ddd, J= 10.1 , 8.2, 1.0 Hz, 1 H), 7.21-7.30 (m, 2H), 3.48 (m, 2H) 2.97-3.09 (m, 2H), 2.94 (d, J=6.8 Hz, 2H), 2.84 (s, 3H), 2.13-2.31 (m, 1 H), 2.02 (m, 2H), 1.53-1.71 (m, 2H); m/z (ES+APCI)⁺: 419 [M+Hf.

Intermediate 6

3-Bromo- V-(1-methylpiperidin-4-yl)imidazo[1,2-b]pyridazin-6-amine

To a solution of 1-methylpiperidine-4-amine (11.8 g, 103 mmol, 3.0 eq) in N- methylpyrrolidinone (32 mL) was added 3-bromo-6-chloroimidazo[1 ,2-J ]pyridazine (8.0 g, 34 mmol, 1.0 eq). The reaction mixture was heated in a microwave at 180°C for 35 min. The reaction mixture was diluted with ethyl acetate (200 mL) and washed with deionised water (3 x 250 mL). The organic layer was separated, dried (MgS0 ), filtered and concentrated in vacuo. Purification by chromatography on silica gel (2.5%-25% 2M NH₃ in eOH/EtOAc) gave a pale yellow solid (4.8 g, 45%); ¹H NMR (400 MHz, MeOD-d,) δ ppm 7.52 (d, J=9.6 Hz, 1 H), 7.37 (s, 1 H), 6.67 (d, J=9.6 Hz, 1H), 3.91-3.66 (m, 1 H), 2.97-2.78 (m, 2H), 2.30 (s, 3H), 2.26-2.08 (m, 4H), 1.79-1.72 (m, 2H); m/z (ES+APCI)⁺ : 310 [M+H]⁺.

Intermediate 7

3-(4-aminophenyI)-W-(1-methy!piperid!n-4-yI)imidazo[1,2- ]pyridazin-6-arnine

Following the method for Intermediate 5 using intermediate 6 and 4-aminophenylboronic acid pinacol ester gave a yellow solid (965 mg, 42%); ¹H NMR (400 MHz, DMSO-cf₆) δ ppm 7.79-7.93 (m, 2H), 7.66 (d, J=9.6 Hz, 1 H), 7.63 (s, 1 H), 6.89 (d, J=6.4 Hz, 1 H), 6.60-6.66 (m, 2H), 6.58 (d, J=9.6 Hz, 1 H), 5.28 (s, 2H), 3.47-3.70 (m, 1 H), 2.77-2.88 (m, 2H), 2.21 (s, 3H), 1.93-2.11 (m, 4H), 1.35-1.59 (m, 2H); m/z (ES+APCI)⁺: 323 [M+HJ⁺. Example 65

3-{4-[(3,5-Difluoropyridin-2-yl)amino]phenyl}-A/-(1-rnethylpiperidin-4-yl)imidazo[1,2- b]pyridazin-6-amine

Following the method for example 16 using intermediate 7 and 2-bromo-3,5- difluoropyridine gave a yellow solid (22 mg, 27%); ¹H NMR (400 MHz, DMSO- /₆) δ ppm 9.02 (d, =1.8 Hz, 1 H), 8.04-8.15 (m, 3H), 7.78-7.89 (m, 4H), 7.72 (d, J=9.6 Hz, 1 H), 6.97 (d, J=6.4 Hz, 1 H), 6.65 (d, J=9.6 Hz, 1 H), 3.51-3.68 (m, 1 H), 2.74-2.85 (m, 2H), 2.20 (s, 3H), 1.98-2.12 (m, 4H), 1.43-1.56 (m, 2H); m/z (ES+APCI)⁺: 436 [M+H]⁺.

Example 66

A/-(1^ethylpiperidin-4-yl)-3-{4-[(6-methylpyridazin-3-yl)amino]phenyl}imidazot1,2- j ]pyridazin-6-amine

Following the method for example 16 using intermediate 7 and 3-chloro-6-methylpyridazine gave a yellow solid (28 mg, 36%); ¹H NMR (400 MHz, DMSO-cfe) δ ppm 9.28 (s, H), 8.04- 8.24 (m, 2H), 7.77-7.90 (m, 3H), 7.72 (d, J=9.6 Hz, 1 H), 7.35 (d, J=9.2 Hz, 1H), 7.08 (d, J=9.2 Hz, 1 H), 6.97 (d, J=6.4 Hz, 1H), 6.65 (d, J=9.6 Hz, 1 H), 3.53-3.71 (m, 1 H), 2.75-2.90 (m, 2H), 2.48 (s, 3H), 2.21 (s, 3H), 1.90-2.14 (m, 4H), 1.36-1.63 (m, 2H); m/z (ES+APCI)⁺: 415 [M+H]⁺.

Example 67

3-{4-[(5-fluoropyrimidin-4-yl)amino]phenyl}-/V-(1 -methylpiperidin-4-yl)imidazo[1 ,2- b] py ri dazi n-6-am i n e

Following the method for example 16 using intermediate 7 and 4-chloro-5-fluoropyrimidine gave a yellow solid (21 mg, 26%); ¹H NMR (400 MHz, DMSO-d₆) δ ppm 9.73 (s, 1H), 8.48 (d, J=2.8 Hz, 1 H), 8.41 (d, J=4.1 Hz, 1 H), 8.10-8.25 (m, 2H), 7.87-7.93 (m, 2H), 7.85 (s, 1 H), 7.74 (d, J=9.6 Hz, 1 H), 7.01 (d, J=6.4 Hz, 1 H), 6.67 (d, J=9.6 Hz, 1 H), 3.51-3.69 (m, 1 H), 2.72-2.89 (m, 2H), 2.21 (s, 3H), 1.98-2.14 (m, 4H), 1.43-1.59 (m, 2H); m/z (ES+APCI)⁺: 419 [M+H]⁺.

Example 68

/V-(1-MethyIpiperidin-4-yl)-3-[4-(pyrazin-2-ylamm^

amine

Following the method for example 16 using intermediate 7 and 2-chloropyrazine gave a yellow solid (22 mg, 29%); ¹H NMR (400 MHz, DMSO-d₆) δ ppm 9.65 (s, 1 H), 8.25 (d, J=1.4 Hz, 1 H), 8.09-8.19 (m, 3H), 7.94 (d, J=2.8 Hz, 1H), 7.76-7.84 (m, 3H), 7.72 (d, J=9.6 Hz, 1 H), 6.98 (d, J=6.9 Hz, 1 H), 6.65 (d, J=9.6 Hz, 1 H), 3.52-3.68 (m, 1 H), 2.74-2.87 (m, 2H), 2.20 (s, 3H), 1.96-2.13 (m, 4H), 1.41-1.59 (m, 2H); m/z (ES+APCI)⁺: 401 [M+H]⁺.

Example 69 3-{6-[(3-Fluoropyridin-2-yl)amino]pyridin-3-yl}-W-[irans-4-(pyrroIidin-1- yl)cyclohexyl]imidazo[1,2-/>]pyridazin-6-amine

a) 3-(6-Aminopyridin-3-yI)-W-[frans-4-(pyrroIidin-1-yl)cyclohexyl]imidazo[1,2- b] pyridazin-6-amine

Following the procedure for intermediate 3, using 3-bromo-/V-4-(pyrrolidin-1-yl)-trans- cyclohexyl)imidazo[1 ,2-b]pyridazin-6-amine (500 mg, 1.37 mmol, 1.0 eq) and 2- aminopyridine-5-boronic acid pinacol ester (452 mg, 2.06 mmol, 1.5 eq) gave a beige solid (468 mg, 90%); H NMR (400MHz, DMSO-d_B) δ ppm 8.76-8.73 (m, 1H), 8.08 (dd, J=2.3, 8.7 Hz, 1 H), 7.70-7.66 (m, 2H), 6.93 (d, J=6.9 Hz, 1 H), 6.59 (d, J=9.6 Hz, 1 H), 6.53 (d, J=8.7 Hz, 1 H), 6.11 (s, 2H), 3.64-3.46 (m, 1 H), 2.88-2.61 (m, 3H), 2.21-2.00 (m, 5H), 1.84- 1.63 (m, 4H), 1.44-1.19 (m, 5H); m/z (ES+APCI)⁺: 378 [M+H]⁺.

b) 3^6-[(3-Fluoropyridin-2-yl)amino]pyridin-3-yl}-W-[irans-4-(pyrroIidin-1- yl)cyclohexyl]imidazo[1,2-6 ridazin-6-amine

A mixture of S-ie-aminopyridin-S-y -W-t.rans^-ipyrrolidin-l-y cyclohexylJimidazoII ^- 6]pyridazin-6-amine (250 mg, 0.66 mmol, 1.0 eq), 2-chloro-3-fluoropyridine (73 μΙ_, 96 mg, 0.73 mmol, 1.1 eq), Pd(OAc)₂ (15 mg, 0.1 eq), Xantphos (38 mg, 0.1 eq), Cs₂C0₃ (860 mg, 2.64 mmol, 4.0 eq) and dioxane (4 mL) was heated at 80°C for 3 h. Additional portions of Pd(OAc)₂ (0.2 eq), Xantphos (0.2 eq) and 2-chloro-3-fluoropyridine (0.5 eq) were added and the mixture heated for a further 2 h, then the mixture was concentrated under reduced pressure and purified by prep-HPLC to give a pale yellow solid (76 mg, 24%); ¹H NMR (400MHz, D SO-cfe) δ ppm 9.37-9.32 (m, 1 H), 9.11 (d, J=1.8 Hz, 1 H), 8.42 (dd, J=2.3, 8.7 Hz, 1H), 8.11-8.06 (m, 2H), 7.88 (s, 1 H), 7.73 (d, J=9.6 Hz, 1 H), 7.67-7.61 (m, 1H), 7.04- 6.96 (m, 2H), 6.66 (d, J=9.6 Hz, 1 H), 3.58 (br. s, 1 H), 2.74-2.51 (m, 3H), 2.19-2.08 (m, J=8.7 Hz, 2H), 2.07-1.96 (m, 3H), 1.72-1.63 (m, 4H), 1.37-1.20 (m, 5H); m/z (ES+APCI)⁺: 473 [M+H]⁺.

Example 70

3-{4-[(3-Fluoropyridin-2-yl)amino]phenyl}-W-[irans-4-(pyrrolidin-1- yl)cyclohexyI]imidazo[1 ,2-/5]pyridazin-6-amine

a) 3-(4-Aminophenyl)-iV-[irans-4-(pyrroIidin-1-yl)cyclohexyl]imidazo[1_J2-b]pyridazin- 6-amine

Following the method for example 54b) using 4-aminophenylboronic acid pinacol ester gave an off-white solid (155 mg, 37%); ¹H NMR (400 MHz, DMSO-cfe) δ ppm 7.81-7.90 (m, 2H), 7.60-7.69 (m, 2H), 6.84 (d, J=6.9 Hz, 1H), 6.59-6.67 (m, 2H), 6.50-6.59 (m, 2H), 5.27 (s, 2H), 2.52-2.61 (m, 3H), 2.09-2.23 (m, 2H), 1.94-2.09 (m, 3H), 1.62-1.74 (m, 4H), 1.13- 1.36 (m, 5H); m/z (ES+APCI)⁺: 377 [M+Hf.

b) 3-{4-[(3-Fluoropyridin-2-y[)amino]phenyl}-/V-[frans-4-(pyrrolidin-1- yl)cyclohexyI]imidazo[1 ,2-f>]pyridazin-6-amine

Following the method for example 16 using 3-(4-aminophenyl)-A/-[frans-4-(pyrrolidin-1- yl)cyclohexyl]imidazo[1 ,2-b]pyridazin-6-amine and 2-chloro-3-fluoropyridine gave an off- white solid (50 mg, 27%); ¹H NMR (400 MHz, DMSO-d₆) δ ppm 8.99 (d, J=1.8 Hz, 1 H), 8.06-8.18 (m, 2H), 8.00 (d, J=5.0 Hz, 1 H), 7.85-7.94 (m, J=9.2 Hz, 2H), 7.80 (s, 1 H), 7.71 (d, J=9.6 Hz, 1 H), 7.57 (ddd, J=1.6, 8.1 , 11.8 Hz, 1 H), 6.94 (d, J=6.9 Hz, 1 H), 6.84 (ddd, J=3.2, 4.8, 8.0 Hz, 1 H), 6.63 (d, J=9.6 Hz, 1 H), 3.51-3.66 (m, 1 H), 2.52-2.58 (m, 3H), 2.11- 2.24 (m, 2H), 1.95-2.10 (m, 3H), 1.61-1.74 (m, 4H), 1.20-1.40 (m, 5H); m/z (ES+APCI)⁺: 472 [M+Hf.

Example 71

W-(1- ethylpiperidin-4-yI)-3-[1 -(pyrazin-2-yI)-1W-pyrazol-4-yl]imidazo[1,2-fe]pyridazin- 6-amine

a) /V-(1-Methylpiperidin-4-yl)-3- 1H-pyrazol-4-y!)imidazo[1 ,2-b]pyridazin-6-amine

A solution of intermediate 6 (1.21 g, 3.92 mmol), PdCI₂(dppf) (640 mg, 0.78 mmol, 0.2 eq), 1-boc-pyrazole-4-boronic acid pinacol ester (3.44 g, 11.7 mmol, 3 eq) and Cs₂C0₃ (5.08 g, 15.6 mmol, 4 eq) in degassed dioxane (20 mL) was stirred at 90°C for 18 h. Concentration in vacuo directly onto silica and purification by chromatography on silica gel (2-22% 2M NH₃/MeOH in EtOAc) afforded a pale brown solid (821 mg, 71 %); ¹H NMR (400 MHz, DMSO-d₆) δ ppm 8.34 (br. s, 1 H), 8.13 (br. s, 1 H), 7.69 (s, 1 H), 7.68 (d, J=9.6 Hz, 1 H), 6.95 (br. d, J=6.9 Hz, 1 H), 6.61 (d, J=9.6 Hz, 1 H), 3.69-3.60 (m, 1 H), 2.82-2.77 (m, 2H), 2.22 (s, 3H), 2.13-2.05 (m, 4H), 1.55-1.46 (m, 2H); m/z (ES+APCIf : 298 [M+H]⁺.

b) W-(1- ethylpiperidin-4-yl)-3-[1-(pyrazin-2-yl)-1W-pyrazol-4-yl]imidazo[1,2- b] pyridazin-6-am i n e

/V-(1-Methylpiperidin-4-yI)-3-(1 H-pyrazol-4-yl)imidazo[1 ,2-b]pyridazin-6-amine (40 mg, 0.13 mmol), copper iodide (8 mg, 0.04 mmol), Cs₂C0₃ (110 mg, 0.34 mmol), 2-chloropyrazine (18 μΙ, 0.20 mmol) were combined in DMF (1 ml), the solvent degassed and the reaction mixture heated at 110°C for 18 h. After cooling, ethyl acetate was added and the reaction mixture was filtered through celite, the solvents were evaporated and purification by prep- HPLC gave the product as a white solid (7 mg, 51%); ¹H NMR (400 MHz, DMSO-d_B) δ ppm 9.39 (s, 1 H), 9.28 (d, J=1.4 Hz, 1 H), 8.65 (d, J=2.3 Hz, 1 H), 8.51 - 8.58 (m, 2H), 7.93 (s, 1 H), 7.76 (d, J=9.6 Hz, 1 H), 7.14 (d, J=6.4 Hz, 1 H), 6.68 (d, J=9.6 Hz, 1 H), 3.64 - 3.74 (m, 1 H), 2.85 (d, J=11.9 Hz, 2H), 2.27 (s, 3H), 2.10-2.23 (m, 4H), 1.46-1.59 (m, 2H); m/z (ES+APCI)⁺: 376 [M + Hf.

Example 72

3-{4-[(3-Fluoro-6-methylpyridin-2-yl)amino]phenyl}-/V-(1-methylpiperidin-4- yl)imidazo[1 ,2-b]pyridazin-6-amine

Following the method for example 16 using intermediate 7 and 2-bromo-3-fluoro-6- methylpyridine gave a yellow solid (20 mg, 15%); ¹H NMR (400 MHz, DMSO-cfe) δ ppm 8.91 (d, J=2.3 Hz, 1 H), 8.05-8.21 (m, 2H), 7.89-8.03 (m, 2H), 7.82 (s, 1H), 7.72 (d, J=9.6 Hz, 1 H), 7.44 (dd, J=8.0, 11.7 Hz, 1 H), 6.98 (d, J=6.4 Hz, 1 H), 6.54-6.76 (m, 2H), 3.48- 3.70 (m, 1 H), 2.77-2.92 (m, 2H), 2.39 (s, 3H), 2.20 (s, 3H), 1.94-2.15 (m, 4H), 1.39-1.58 (m, 2H); m/z (ES+APCI)⁺: 432 [M+H]⁺.

Example 73

3-{4-[(5-Chloro-3-fluoropyridin-2-yl)amino]pheny>}- V-(1-methylpiperidin

yl)imidazo[1,2-b]pyridazin-6-amine

Following the method for example 16 using intermediate 7 and 2,5-dichloro-3- fluoropyridine gave a yellow solid (45 mg, 32%); ¹H NMR (400 MHz, DMSO- ₆) δ ppm 9.18 (d, J=1.8 Hz, 1 H), 8.02-8.22 (m, 3H), 7.77-7.97 (m, 4H), 7.72 (d, J=9.6 Hz, 1 H), 6.97 (d, J=6.4 Hz, 1 H), 6.65 (d, =9.6 Hz, 1H), 3.51-3.73 (m, 1H), 2.72-2.91 (m, 2H), 2.21 (s, 3H), 1.95-2.13 (m, 4H), 1.35-1.61 (m, 2H); m/z (ES+APCI)⁺: 452 [M+H]⁺.

Example 74

3-[3,5-Difluoro-4-(pyridin-2-ylamino)phenyl]-A/-(1-methyIpiperidin-4-yl)imidazo[1,2- b]pyridazin-6-amine

a) 2,6-DifIuoro-4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)aniline

A solution of 4-bromo-2,6-difluoroaniline (2.50 g, 12.02 mmol, 1.0 eq), bis(pinacolato)diboron (3.36 g, 13.22 mmol, 1.1 eq), Pd(dppf)CI₂ (150 mg, 0.18 mmol, 15 mol %) and potassium acetate (3.54 g, 36.06 mmol, 3.0 eq) in DMSO was heated at 80°C under nitrogen for 90 minutes. The reaction mixture was partitioned between EtOAc (100 mL) and saturated aqueous bicarbonate (100 ml_). The organic layer was washed with brine (3 x 100 mL), dried over MgS0₄ and concentrated in vacuo to give a brown solid (3.0 g, 97%); H NMR (400 MHz, DMSO-d₆) δ ppm 6.94-7.07 (m, 2H), 5.66 (s, 2H), 1.17-1.28 (m, 12H); m/z (ES+APCI)⁺: 256 [M+H]⁺.

b) 3-(4-Amino-3,5-difluorophenyl)-W-(1 -methylpiperidin-4-yl)imidazo[1 ,2-fa]pyridazin- 6-amine

Following the method for intermediate 5 using 3-bromo-A/-(1-methylpiperidin-4- yl)imidazo[1 ,2-b]pyridazin-6-amine and 2,6-difluoro-4-(4,4,5,5-tetramethyl-1 ,3,2- dioxaborolan-2-yl)aniline gave a yellow solid (521 mg, 45%); H NMR (400 MHz, DMSO- d₆) δ ppm 7.80-7.96 (m, 3H), 7.71 (d, J=9.6 Hz, 1 H), 7.05 (d, J=6.9 Hz, 1 H), 6.64 (d, J=9.6 Hz, 1 H), 5.40 (s, 2H), 3.42-3.67 (m, 1 H), 2.76-2.91 (m, 2H), 2.19 (s, 3H), 1.94-2.15 (m, 4H), 1.34-1.59 (m, 2H); m/z (ES+APCI)*: 359 [M+H]⁺.

c) 3-[3,5-Difluoro-4-(pyridin-2-yIamino)phenyl]-W-(1-methyIpiperidin-4-yl)imid b]pyridazin-6-amine

Following the method for example 16 using 2,6-difluoro-4-(4,4,5,5-tetramethyl-1 ,3,2- dioxaborolan-2-yl)aniline and 2-chloropyridine gave a yellow solid (11 mg, 9%); ¹H NMR (400 MHz, DMSO-de) δ ppm 8.54 (s, 1 H), 8.00-8.07 (m, 3H), 7.98 (dd, _/=1.4, 5.0 Hz, 1 H), 7.75 (d, J=9.6 Hz, 1 H), 7.52 (ddd, J=1.8, 7.0, 8.6 Hz, 1 H), 7.13 (d, J=6.4 Hz, 1 H), 6.60-6.77 (m, 3H), 3.43-3.67 (m, 1 H), 2.69-2.93 (m, 2H), 2.16 (br. s, 3H), 1.92-2.12 (m, 4H), 1.32- 1.61 (m, 2H); m/z (ES+APCI)⁺: 436 [M+H]⁺.

Intermediate 8

fert-Butyl (irans-4-{[3-(4-aminophenyl)imidazo[1 ,2- }]pyridazin-6- yl]amino}cyclohexy[)carbamate

Following the method for intermediate 5, using Intermediate 1 and 4-aminophenylboronic acid pinacol ester gave a yellow solid (685 mg, 66%); H NMR (400 MHz, DMSO-cfe) δ ppm 7.76-7.95 (m, 2H), 7.65 (d, J=9.6 Hz, 1 H), 7.58-7.63 (m, 1 H), 6.84 (d, J=6.9 Hz, 1 H), 6.79 (s, 1H), 6.59-6.70 (m, 2H), 6.56 (d, J=10.1 Hz, 1 H), 5.26 (s, 2H), 3.42-3.64 (m, 1 H), 3.13- 3.39 (m, 1H), 2.10-2.24 (m, 2H), 1.76-1.93 (m, 2H), 1.39 (s, 9H), 1.17-1.35 (m, 4H); m/z (ES+APCI)⁺; 423 [M+H]⁺.

Example 75

irans-W-(3-{4-[(3-Fluoropyridin-2-yl)amino]phenyl}imidazo[1,2-/3]pyridazin-6- yl)cyclohexane-1 ,4-diamine

Following the method for example 16 using intermediate 8 and 2-chloro-3-fluoropyridine gave a yellow solid (25 mg, 17%); ¹H NMR (400 MHz, DMSO-d₆) δ ppm 9.00 (d, J=1.8 Hz, 1 H), 8.07-8.15 (m, 2H), 7.97-8.05 (m, 1 H), 7.85-7.93 (m, 2H), 7.79 (s, 1 H), 7.70 (d, J=9.6 Hz, 1H), 7.57 (ddd, J=1.6, 8.1 , 11.8 Hz, 1 H), 6.89 (d, J=6.9 Hz, 1 H), 6.83 (ddd, J=3.2, 4.8, 8.0 Hz, 1 H), 6.63 (d, J=9.6 Hz, 1 H), 3.46-3.61 (m, 1H), 2.55-2.69 (m, 1 H), 2.09-2.19 (m, 2H), 1.79-1.90 (m, 2H), 1.10-1.34 (m, 4H); m/z (ES+APCIf: 418 [M+H]⁺.

Example 76

irans-W-(3^4-[(3,5-Difluoropyridin-2-yl)amino]phenyl}imidazo[1,2-il)]pyridazin-6- yl)cyclohexane-1 ,4-diamine

Following the method for example 16 using Intermediate 8 and 2-bromo-3,5- difluoropyridine gave a yellow solid (49 mg, 31 %); ¹H NMR (400 MHz, DMSO-d₆) δ ppm 9.03 (d, J=1.8 Hz, 1H), 8.04-8.16 (m, 3H), 7.78-7.89 (m, 4H), 7.70 (d, J=9.6 Hz, 1 H), 6.90 (d, J=6.9 Hz, 1 H), 6.62 (d, J=9.6 Hz, 1 H), 3.48-3.60 (m, 1 H), 2.57-2.68 (m, 1 H), 2.10-2.19 (m, 2H), 1.80-1.90 (m, 2H), 1.13-1.32 (m, 4H); m/z (ES+APCI)⁺: 436 [M+H]⁺.

Example 77

irans-W-iS^-iiS-Chloro-S-fluoropyridin^-ylJaminolphenyl^midazoII.Z-bJpyridazin-e- yl)cyclohexane-1 ,4-diamine

Following the method for example 16 using intermediate 8 and 2,5-dichloro-3- fluoropyridine gave a yellow solid (21 mg, 13%); ¹H NMR (400 MHz, DMSO-d₆) δ ppm 9.19 (d, J=1.8 Hz, 1 H), 8.05-8.18 (m, 3H), 7.77-7.90 (m, 4H), 7.71 (d, J=10.1 Hz, 1 H), 6.91 (d, J=6.9 Hz, 1 H), 6.63 (d, J=9.6 Hz, 1 H), 3.43-3.62 (m, 1 H), 2.57-2.72 (m, 1 H), 2.08-2.21 (m, 2H), 1.76-1.91 (m, 3H), 1.13-1.33 (m, 4H); m/z (ES+APCI)⁺: 452 [M+H]⁺.

Example 78

frans-A/-(3-{4-[(3-Fluoro-6-methylpyridin-2-^

6-yl)cyclohexane-1 ,4-diamine

Following the method for example 16 using intermediate 8 and 2-bromo-3-fluoro-6- methylpyridine gave a yellow solid (24 mg, 16%); ¹H NMR (400 MHz, DMSO-d₆) δ ppm 8.91 (d, J=1.8 Hz, 1 H), 8.03-8.19 (m, 2H), 7.86-8.03 (m, 2H), 7.81 (s, 1 H), 7.70 (d, J=9.6 Hz, 1 H), 7.43 (dd, J=7.8, 11.45 Hz, 1 H), 6.91 (d, J=6.4 Hz, 1 H), 6.55-6.72 (m, 2H), 3.46- 3.63 (m, 1 H), 2.57-2.70 (m, 1 H), 2.38 (s, 3H), 2.11-2.25 (m, 2H), 1.81-1.92 (m, 2H), 1.14- 1.39 (m, 4H), m/z (ES+APCI)⁺: 432 [M+H]⁺.

Example 79 A/-(1-Methylpiperidin-4-yl)-3-(4-{[5-(trifluoromethyl)pyridin-2- yl]amino}phenyl)imidazo 1,2-b]pyridazin-6-amine

A mixture of intermediate 6 (100 mg, 0.31 mmol, 1.0 eq), 2-chloro-5-trifluoromethylpyridine (67 mg, 0.37 mmol, 1.2 eq), Pd(OAc)₂ (14 mg, 0.2 eq), Xantphos (36 mg, 0.2 eq), Cs₂C0₃ (303 mg, 0.93 mmol, 3.0 eq) and dioxane (1.5 ml_) was heated at 90°C for 3 h. The mixture was allowed to cool, then applied to an Isolute SCX cartridge and eluted with MeOH then 2M NH₃ in MeOH, concentrated under reduced pressure and purified by prep-HPLC. This gave the product as an off-white solid (10 mg, 7%); Ή NMR (400MHz, MeOD-d,) δ ppm 8.45-8.40 (m, 1 H), 8.13-8.06 (m, 2H), 7.79-7.68 (m, 4H), 7.61 (d, J=9.6 Hz, 1 H), 6.92 (d, J=8.7 Hz, 1 H), 6.68 (d, J=9.6 Hz, 1H), 3.84-3.74 (m, 1H), 2.99-2.90 (m, 2H), 2.36 (s, 3H), 2.33-2.16 (m, 4H), 1.72-1.57 (m, 2H); m/z (ES+APCI)⁺: 468 [M+H]⁺.

Example 80

3-(4^[3-Fluoro-6-(trifluoromethyl)pyridin-2-yl]amino}phenyl)-W-(1-methylpiperidin yl)imidazo[1 ,2-b]pyridazin-6-amine

Following the procedure for example 79 using 2-chloro-6-trifluoromethylpyridine (67 mg, 0.37 mmol, 1.2 eq) gave an off-white solid (17 mg, 12%); ¹H NMR (400MHz, MeOD-cf₄) δ ppm 8.06-8.01 (m, 2H), 7.91-7.85 (m, 2H), 7.76-7.70 (m, 2H), 7.67 (d, J=9.6 Hz, 1 H), 7.14 (d, J=7.3 Hz, 1 H), 7.03 (d, J=8.7 Hz, 1 H), 6.70 (d, J=9.6 Hz, 1 H), 4.05-3.95 (m, 1 H), 3.57- 3.40 (m, 2H), 3.21-3.01 (m, 2H), 2.83 (s, 3H), 2.53-2.38 (m, 2H), 1.99-1.69 (m, 2H) m/z (ES+APCI)⁺: 468 [M+H]⁺. Example 81

3-(4 [3-Fluoro-5-(trifluoromethyl)pyridin-2-yl]amino}phenyI)-W-(1-methylpiperidin-4- yl)imidazo[1,2-6]pyridazin-6-amine

Following the procedure for example 79 using 2-bromo-3-fluoro-5-trifluoromethylpyridine (91 mg, 0.37 mmol, 1.2 eq) gave a yellow solid (21 mg, 14%); ¹H NMR (400MHz, DMSO- d„) δ ppm 9.57 (s, 1 H), 8.37 (s, 1 H), 8.19-8.11 (m, 2H), 8.02 (dd, J=1.8, 11.4 Hz, 1 H), 7.92- 7.87 (m, J=9.2 Hz, 2H), 7.84 (s, 1 H), 7.73 (d, J=9.6 Hz, 1 H), 6.99 (d, J=6.4 Hz, 1 H), 6.66 (d, J=9.6 Hz, 1 H), 3.65-3.54 (m, 1H), 2.84-2.75 (m, 2H), 2.20 (s, 3H), 2.11-1.99 (m, 4H), 1.57-1.43 (m, 2H); m/z (ES+APCI)⁺: 486 [ +Hf.

PfCDPKI Assay Biochemical Assay

Selected compounds of the invention were assessed in a PfCDPKI assay to measure the inhibition of PfCDPKI phosphorylation of the endogenous substrate. All assays were carried out at room temperature (~21 °C) and were linear with respect to time and enzyme concentration under the conditions used. Assays were performed for up to 180 min in a 384 well format. PfCDPKI was present at a concentration of 20-50 nM. The enzyme was diluted and assayed in 50 mM Tris-HCI pH8, 0.1 mM EGTA, 1 mM DTT, 20 mM MgCl_z and 0.01 % Triton X- 00. The physiological substrate, MTIP, was used in the assay at K_m (8 μΜ). ATP was at K_m (10 μΜ), 0.2 mM CaCI₂ was used to initiate the reaction, and the reaction was stopped by the addition of Promega's Kinase-Glo Plus® reagent. A luminescence signal is generated that is proportional to the amount of ATP remaining at the end of the kinase reaction. The 384 well plates are read on the BMG LABTECH Pherastar (BMG LABTECH LTD, PO Box 73, Aylesbury, HP20 2QJ). IC₅₀ values of inhibitors were determined after carrying out assays at 10 different concentrations of each compound in duplicate under the same conditions.

PfCDPKI IC_5D values (in μΜ) for selected compounds of the invention are shown in Table 1. Compounds with lower IC₅₀ values are more potent inhibitors.

Parasite cell-based assay (FACS EC₅₀)

The efficacy of selected compounds of the invention was assessed using an in vitro model of malaria parasite growth which measures merozoite invasion of red blood cells. Compounds with lower EC₅₀ values are more potent inhibitors of merozoite invasion of red blood cells (and should therefore be more effective treatments for malaria). The EC₅₀ value is the concentration of compound which reduces malaria growth by 50% over a control.

Test cultures were set up at 0.5% parasitaemia and 2% haematocrit, from a synchronized stock culture of 3D7 P. falciparum. Compounds were diluted into 2% DMSO and added to 95 pL parasite culture in a 96-well plate and incubated under static conditions. Compounds were tested in duplicate and were added to parasites approximately 24 hours post-invasion. Cells were recovered 48 hours later and processed for FACS analysis as described by Bergmann-Leitner et al. Briefly, 50 pl_ of the parasite culture was transferred into a polystyrene FACS tube and stained with 500 μΙ_ of 500 pg/mL hydroethidine (HE) in PBS. The parasites were incubated for 20 min at 37°C, then diluted with 1 imL PBS and stored on ice prior to FACS analysis. The data was acquired using CellQuest Pro software on a FACSCalibur (Becton Dickinson). Growth inhibition was calculated using the following formula:

% growth inhibition = (1 -[parasitaemia of culture/parasitaemia of control culture]) ^χ 100. Bergmann-Leitner et a/. Critical evaluation of different methods for measuring the functional activity of antibodies against malaria blood stage antigens. Am J Trap Med Hyg (2006) vol. 75 (3) pp. 437-42. EC₅₀ values (in μΜ) for selected compounds of the invention are shown in Table 2.

Cytotoxicity Studies

The cytotoxicity of the compounds of the invention was assessed by measuring cell viability in an assay of cell death. Cells tested are HepG2 cells. A higher value indicates a safer compound.

Hep G2 cells were plated into 96 well plates with Minimum Essential Media Eagles (EMEM, Sigma), 10% FBS, 2 mM Glutamax and 1X NEAA and incubated overnight. Compounds were diluted and added to the assay plates using the Biomek Fx, with the final DMSO concentration at 0.1 % v/v. The cells were incubated for 48 h before cytotoxicity levels were measured using CellTiter Blue Cell Viability Assay and Cytotox-ONE homogeneous membrane integrity Assay (Promega).

IC₅₀ values of inhibitors were determined after carrying out assays at 10 different concentrations of each compound in duplicate under the same conditions

HL

Human Microsomal Turnover Protocol

HLM values were measured for selected compounds of the invention (see Table 2). HLM (% rem) is a measure of compound metabolism in human liver microsomes. The number quoted is the % of parent compound still intact after 40 minutes incubation in the presence of human liver microsomes. Compounds with higher % rem are more stable and should therefore have better half lives in vivo. The compounds (1 μΜ) were incubated with pooled human liver microsomes (0.25 mg protein/mL) at 37°C in 0.5M potassium phosphate buffer pH 7.4. The reactions were initiated by the addition of NADPH co-factor generating solution* previously incubated at 37°C for 0 minutes. Samples were taken at 0 and 40 minutes and the reaction terminated by the addition of 2 times volume of methanol at 4°C containing an internal standard. The samples were centrifuged at 10000 rpm for 10 minutes and the resultant supernatant analyzed for disappearance of parent compound by mass spectrometry (LC-MS/MS). LM

Mouse Microsomal Turnover Protocol

MLM values were measured for selected compounds of the invention (see Table 2). MLM (% rem) is a measure of compound metabolism in mouse liver microsomes. The number quoted is the % of parent compound still intact after 30 minutes incubation in the presence of mouse liver microsomes. Compounds with higher % rem are more stable and should therefore have better half lives in vivo.

The compounds (1 μΜ) were incubated with pooled mouse liver microsomes (0.1 mg protein/mL) at 37°C in 0.5M potassium phosphate buffer pH 7.4. The reactions were initiated by the addition of NADPH co-factor generating solution* previously incubated at 37°C for 10 minutes. Samples were taken at 0 and 30 minutes and the reaction terminated by the addition of 2 times volume of methanol at 4°C containing an internal standard. The samples were centrifuged at 10000 rpm for 10 minutes and the resultant supernatant analyzed for disappearance of parent compound by mass spectrometry (LC-MS/MS).

* Assay concentration NADPH generating reagents -1.3mM NADP+, 3.3mM glucose-6- phosphate, 0.4U/mL glucose-6-phosphate dehydrogenase and 3.3mM magnesium chloride. Various modifications and variations of the described aspects of the invention will be apparent to those skilled in the art without departing from the scope and spirit of the invention. Although the invention has been described in connection with specific preferred embodiments, it should be understood that the invention as claimed should not be unduly limited to such specific embodiments. Indeed, various modifications of the described modes of carrying out the invention which are obvious to those skilled in the relevant fields are intended to be within the scope of the following claims. REFERENCES

Baum et al. A conserved molecular motor drives cell invasion and gliding motility across malaria lifecycle stages and other apicomplexan parasites. J Biol Chem (2006a) vol 281 (8) pp. 5197-208;

Baum et al. Regulation of apicomplexan actin-based motility. Nat Rev Microbiol (2006b) vol. 4 (8) pp. 621-8;

Green et al. The MTIP-myosin A complex in blood stage malaria parasites. J Mol Biol

(2006) vol 355(5) pp. 933-41 ;

Ishino et al. A calcium-dependent protein kinase regulates Plasmodium ookinete access to the midgut epithelial cell. Mol Microbiol (2006) vol. 59 (4) pp. 1175-84;

Kieschnick et al. Toxoplasma gondii attachment to host cells is regulated by a calmodulin- like domain protein kinase. J Biol Chem (2001) vol. 276 (15) pp. 12369-77;

Moskes et al. Export of Plasmodium falciparum calcium-dependent protein kinase 1 to the parasitophorous vacuole is dependent on three N-terminal membrane anchor motifs. Mol

Microbiol (2004) vol. 54 (3) pp. 676-91 ;

Pfitzer et al. Invited review: regulation of myosin phosphorylation in smooth muscle. J Appl Physiol (2001) vol. 91 (1) pp. 497-503;

Rees-Channer et al. Dual acylation of the 45 kDa gliding-associated protein (GAP45) in Plasmodium falciparum merozoites. (2006) Mol Biochem Parasitol (2006) vol 149(1) pp. 113-6;

Ryder et al. Enhanced skeletal muscle contraction with myosin light chain phosphorylation by a calmodulin-sensing kinase. J Biol Chem (2007) vol. 282 (28) pp. 20447-54;

Siden-Kiamos et al. Plasmodium berghei calcium-dependent protein kinase 3 is required for ookinete gliding motility and mosquito midgut invasion. Mol Microbiol (2006) vol. 60 (6) pp. 1355-63.

Table 1 : PfCDPKI IC₅₀ values for selected compounds of the invention

"A" denotes an IC₅₀ value against PfCDPKI of less than about 50 nM;

"B" denotes an IC₅₀ value against PfCDPKI of from about 50 nM to about 100 nM; "C" denotes an IC₅₀ value against PfCDPKI of from about 100 nM to about 500 nM.

Table 2: PfCDPKI IC₅₀ values, EC₅₀ values, cytotoxicity (μΜ), HLM, MLM values (% rem)

Example IC50 (μΜ) Cytotoxicity Anti- HLM (% MLM (%

IC50 (uM) parasite rem) rem)

EC50 (μΜ)

6 0.008 6.84 0.047 99 93

7 0.010 >20 0.173 100 89

9 0.014 >20 0.138 98 97

10 0.015 >20 0.106 98 87

14 0.008 >20 0.012 93 85

15 0.008 4.96 0.191 91 96

17 0.010 4.52 0.185 97 95

24 0.012 2.86 0.287 82 60

26 0.010 >20 0.028 89 76

27 0.013 5.89 0.032 98 85 0.009 >20 0.657 83 86

0.013 2.95 0.022 84 99

0.015 5.07 0.014 83 85

0.014 4.21 0.081 69 93

0.014 >20 0.040 75 86

0.014 >20 0.079 80 88

0.021 6.94 0.164 97 86

0.036 1.83 0.160 78 82

0.008 3.20 0.183 83 91

0.009 5.61 0.036 83 81

0.016 3.16 0.407 80 47

0.014 >20 0.097 98 91

0.015 3.43 0.200 78 58

0.019 >20 0.297 71 88

0.016 >20 0.294 60 82

0.031 >20 0.366 66 51

0.019 3.20 0.097 77 52

0.014 1.65 0.046 81 85

Claims

1. A compound of formula I, or a harmaceutically acceptable salt or ester thereof,

(I)

wherein:

R¹ is -(CH₂)_nNR³R⁴, -OR⁵ or -(CH₂)_n-heterocycloalkyl, wherein said heterocycloalkyi group is optionally substituted by one or more R⁷ groups;

R³ is H or alkyl;

R⁴ is:

(i) cycloalkyl optionally substituted by one or more -NR¹¹R¹² or NHCOR ¹ groups; or

(ii) -(CH₂)_n-heterocycloalkyl, wherein said heterocycloalkyi is a 4, 5 or 6-membered nitrogen-containing group optionally containing one or more CO groups, wherein said heterocycloalkyi is optionally substituted by one or more one or more (CH_z)_nR⁷ groups; or

(iii) alkyl substituted by one or more -NR¹¹R¹²groups; or

R³ and R⁴are linked together with the nitrogen to which they are attached to form a 4, 5, 6 or 7-membered monocyclic heterocycloalkyi group or a bicyclic heterocycloalkyi group, each of which optionally contains one or two further groups selected from CO, O, N and S, and which is optionally further substituted by one or more R⁷ groups;

each R⁷ is independently selected from -(CH₂)„NR¹¹R¹², halo, CN, nitro, -COR¹¹, - CONR¹¹R¹², alkyl, haloalkyl, haloalkyoxy, -OR¹¹, -NHC0₂R¹¹, -NHCOR¹¹, -NHS0₂R¹¹ and - C0₂R¹¹; each R⁸ is independently selected from -NR^1BR¹⁷, -OR¹⁷ and -(CH_z)_nR¹⁷ where each R^1B is H and each R¹⁷ is independently -(CHR¹⁰)_n-heteroaryl, wherein said heteroaryl group is in turn optionally substituted by one or more R⁷ groups;

each R¹⁰, R¹¹ and R¹² is independently H or alkyl; or in the case of an -NR¹¹R¹² group, R¹ and R¹² may be linked together with the nitrogen to which they are attached to form a 4, 5,

6 or 7-membered monocyclic or bicyclic heterocycloalkyi group optionally containing one or two further groups selected from CO, O, N and S, and which is optionally further substituted by one or more R⁷ groups;

each m is independently an integer from 1 to 6; and

each n is independently an integer from 0 to 6.

2. A compound according to claim 1 wherein R² is a heteroaryl group or a fused aryl- heterocycloalkyl group, each of which is substituted by at least one R⁸ group, and optionally further substituted by one or more R⁷ groups, and wherein said heterocycloalkyi group is a 5 or 6-membered nitrogen-containing group optionally containing one or more CO groups.

3. A compound according to any preceding claim wherein R² is a heteroaryl group substituted by at least one R^s group, and optionally further substituted by one or more R⁷ groups.

4. A compound according to any preceding claim wherein R² is:

(i) a pyrimidinyl group substituted by one or more R^a groups;

(ii) a pyridinyl group substituted by one or more R⁸ groups;

(iii) a phenyl group substituted by by one or more R^s groups;

(iv) an indolyl group substituted by one or more R⁸ groups;

(v) an indazolyl group substituted by one or more R⁸ groups;

(vi) a benzimidazolyl group substituted by one or more R⁸ groups;

(vii) a pyrazolyl group substituted by one or more R⁸ groups;

(viii) a pyrazolopyridinyl group substituted by one or more R⁸ groups; or

(ix) a fused aryl-heterocycloalkyl group which is

substituted by one or more R groups.

5. A compound according to any preceding claim wherein R² is a pyrimidinyl group substituted by at least one R⁸ group, and optionally further substituted by one or more R⁷ groups.

6. A compound according to any preceding claim wherein R² is a pyrimidinyl group substituted by one or more groups selected from -NR¹⁶R¹⁷ and -OR¹⁷, wherein R¹⁶ is H and R¹⁷ is (CH₂)_n-heteroaryl, wherein said heteroaryl is selected from pyrimidinyl, pyridinyl, pyrazolyl, pyrazinyl, pyridazinyl, quinolinyl, isoquinolinyl, quinazolinyl and quinoxalinyl, each of which is optionally further substituted by one or more R⁷ groups.

7. A compound according to any preceding claim wherein R² is a pyrimidinyl group substituted by one or more groups selected from -NR ^SR¹⁷ and -OR¹⁷, wherein R¹⁶ is H and R¹⁷ is (CH₂)_n-heteroaryl, wherein said heteroaryl is selected from pyrimidinyl, pyridinyl, pyrazolyl, pyrazinyl, pyridazinyl, quinolinyl, isoquinolinyl, quinazolinyl and quinoxalinyl, each of which is optionally further substituted by one or more substituents selected from alkyl, halo and haloalkyl.

8. A compound according to any preceding claim wherein R² is a pyrimidinyl group substituted by one or more -NR¹⁶R¹⁷ groups.

9. A compound according to any preceding claim wherein R² is a pyrimidin-5-yl group substituted in the 2-position by an -NR¹⁶R¹⁷ group.

10. A compound according to any preceding claim wherein R¹ is -NR³R⁴, R³ is H and R is:

(i) cyclohexyl substituted by one or more groups selected from -NR ¹R¹², and - NHCOR¹ ; (ii) -(CH₂)_n-heterocycloalkyl, wherein said heterocycloalkyl is a piperidinyl, pyrrolidinyl or azetidinyl group, each of which is optionally substituted by one or more (CH₂)_nR⁷ groups; or

(iii) alkyl substituted by one or more -NR¹¹R¹² groups; or

11. A compound according to any preceding claim wherein R¹ is -NR³R⁴, R³ is H and R⁴ is selected from the followin :

12. A compound according to any preceding claim wherein R¹ is -NR³R⁴, R³ is H and R⁴ is:

13. A compound according to any one of claims 1 to 10 wherein R¹ is -NR³R⁴, and R³ and R⁴ are linked together to form a group selected from the following:

14. A compound according to any one of claims 1 to 10 wherein R¹ is OR⁵ and R⁵ is selected from the following:

A com ound according to claim 1 which is selected from the following

Structure Example

21

22

23

24

25

Structure Example

81

16. A pharmaceutical composition comprising at least one compound according to any one of claims 1 to 15 and a pharmaceutically acceptable carrier, diluent or excipient.

17. A compound according to any one of claims 1 to 15 for use in medicine.

18. A compound of formula I, as defined in any one of claims 1 to 15, for use in treating or preventing a disorder associated with CDPK.

19. A compound for use according to any one of claims 1 to 15 wherein the disorder associated with CDPK is malaria.

20. Use of a compound of formula I, as defined in any one of claims 1 to 15, in an assay for identifying further candidate compounds capable of inhibiting a CDPK.

21. Use according to claim 20 wherein said assay is a competitive binding assay that comprises contacting a compound of formula I, as defined in any one of claims 1 to 15, with a CDPK and a candidate compound and detecting any change in the interaction between the compound of formula I and the CDPK.

22. A combination comprising a compound of formula 1 as defined in any one of 1 to 15 and a further therapeutic agent.

23. A pharmaceutical composition according to claim 16 which further comprises a second therapeutic agent.

24. A process for preparing a compound of formula (Ic), wherein R¹ is -NR³R⁴ or -OR⁵ and R^z is

(II) (III) (Ic)

(ii) converting said intermediate compound of formula (III) to a compound of formula

(I)-