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Definitions

• Amyloidosis is a diverse group of disease processes characterized by extracellular tissue deposits, in one or many organs, of protein materials which are generically termed amyloid. Amyloid may be distinguished grossly by a starch-like staining reaction with iodine (thus the term amyloid), microscopically by its extracellular distribution and tinctorial and optical properties when stained with Congo red, and by its protein fibril structure as shown by electron microscopy and x- ray crystallography (see Table-1).
• Exemplary amyloidosis diseases are Alzheimer's Disease (“AD”), Down's Syndrome, Type 2 diabetes mellitus, and mild cognitive impairment (MCI).
• AD Alzheimer's disease
• McKhann et al Neurology 34: 939 (1984). It is the most common cause of dementia in the United States. AD can strike persons as young as 40-50 years of age, yet, because the presence of the disease is difficult to determine without dangerous brain biopsy, the time of onset is unknown. The prevalence of AD increases with age, with estimates of the affected population reaching as high as 40-
• AD is characterized by the presence of neuritic plaques (NP), neurofibrillary tangles (NFT), and neuronal loss, along with a variety of other findings. Mann, Meek Ageing Dev. 31: 213 (1985). Post-mortem slices of brain tissue of victims of AD exhibit the presence of amyloid in the form of proteinaceous extracellular cores of the neuritic plaques that are characteristic of AD. The amyloid cores of these neuritic plaques are composed of a protein called the ⁇ -amyloid (A ⁇ ) that is arranged in a predominately beta-pleated sheet configuration. AD is believed to afflict some 4 million Americans and perhaps 20-30 million people worldwide. AD is recognized as a major public health problem in developed nations.
• a ⁇ ⁇ -amyloid
• AD cholinesterase inhibitors
• cholinesterase inhibitors have been approved for the symptomatic treatment of patients with AD - tacrine (Cognex, Warner-Lambert, Morris Plains, New Jersey); donepezil (Aricept, Eisai, Inc., Teaneck, New Jersey, and Pfizer, Inc., New York, New York); rivagstigmine (Exelon, Novartis, Basel, Switzerland); and galantamine (Reminyl, Janssen, Titusville, New Jersey).
• AD therapies that are currently being developed involve immunotherapy, secretase inhibitors or anti-inflammatory drugs. However, to date, there are no available drugs proven to modify the course of cognitive decline.
• a major hurdle to developing anti-amyloid therapies is exemplified by the following quote from (Hock, C. et al., 2003, Neuron, 38:547-554), directed to use of immunotherapy as an anti-amyloid therapy: "[w]e do not know whether brain A ⁇ - amyloid load was reduced in our study patients; in vivo imaging techniques will be required to answer this question.”
• the ability to quantify amyloid load before treatment and then follow the effects of treatment is critical to the efficient development of this class of drugs.
• the present invention employs amyloid imaging as a surrogate marker of efficacy for anti-amyloid therapies.
• the present invention is directed to a method of determining the efficacy of therapy in the treatment of amyloidosis, comprising:
• Z is S, NR', O or C(R') 2 , such that when Z is C(R') 2 , the tautomeric form eterocyclic ring may form an indole:
• R' is H or a lower alkyl group
• Y is NR 1 R 2 , OR 2 , or SR 2 ,
• M is selected from the group consisting of Tc and Re;
• the anti-amyloid agent comprises one or more antibodies against A ⁇ peptide.
• the anti-amyloid agent comprises one or more inhibitors of ⁇ - and/or ⁇ -secretase.
• the anti-amyloid agent comprises a small molecule that binds to A ⁇ l-42, such as a decoy peptide.
• amyloidosis is AD.
• the amyloidosis is an amyloid deposition disorder, wherein a preferred embodiment encompasses amyloidosis which is an amyloid plaque deposition disorder.
• the imaging is selected from the group consisting of gamma imaging, magnetic resonance imaging, and magnetic resonance spectroscopy.
• the imaging is done by gamma imaging, and the gamma imaging is PET or SPECT.
• the compound of Formula (I) is:
• the compound of Formula (I) contains a C label.
• the anti-amyloid agent is a peripheral sink agent.
• PIB 2-[4'-(methylamino)phenyl]6-hydroxy-benzothiazole
• FIG. 2 shows A ⁇ 42 immunoreactivity (ir) and X-34 histofluorescent labeling of ⁇ -pleated sheet in the temporal cortex of AD patients 572 (A 5 D) and 5180 (B 3 E), compared to a representative end-stage AD patient (C 5 F).
• Scale bar 200 ⁇ m. Large areas devoid of plaques in case 572 are marked with asterisks. Case 5180 is devoid of plaques, but shows some neurofibrollary tangles and neuritic elements stained by X- 34.
• FIG. 3 shows A ⁇ 42 immunoreactivity and X-34 histofluorescent labeling of ⁇ - pleated sheet in the frontal cortex of patients 572 (A 5 D) and 5180 (B 5 E) 5 compared to a representative end-stage Alzheimer's disease patient.
• Scale bar 200 ⁇ m. Areas devoid of plaques in case 572 are marked with asterisks. Case 5180 is devoid of plaques, but shows some neurofibrollary tangles stained by X-34 (see Figure 4).
• FIG. 5 The top graph charts ELISA data for A ⁇ 42 in cases 572 and 5180 in frontal, parietal, temporal and cerebellar cortices. These are compared to published data for the frontal, parietal and temporal cortices of elderly controls and AD subjects (Naslund et al. 2000, Jama 283, 1571-1577).
• the present invention is directed to a method for determining the efficacy of therapy in the treatment of amyloidosis.
• the method involves the use of amyloid imaging as a surrogate marker.
• Surrogate markers are a special type of biomarker that may be used in place of clinical measurements as a clinical endpoint for drug approval purposes.
• the methods described herein are useful in drug development trials. For example, the measurement of cholesterol levels is now an accepted surrogate marker of atherosclerosis.
• the methods are clinically useful in assisting patient management decisions. In that regard, quantitative evaluations of amyloid burden can improve clinical decisions concerning drug dose or treatment selections.
• the present invention involves the use of amyloid imaging as a surrogate marker of efficacy for anti-amyloid therapies.
• amyloidosis refers to a disease associated with amyloid deposition, such as Alzheimer's Disease, Down's Syndrome, Type 2 diabetes mellitus, hereditary cerebral hemorrhage amyloidosis (Dutch), amyloid A (reactive), secondary amyloidosis, MCI, familial Mediterranean fever, familial amyloid nephropathy with urticaria and deafness (Muckle-wells Syndrome), amyloid lambda L-chain or amyloid kappa L-chain (idiopathic, myeloma or macroglobulinemia-associated) A beta 2M (chronic hemodialysis), ATTR (familial amyloid polyneuropathy (Portuguese, Japanese, Swedish)), familial amyloid cardiomyopathy (Danish), isolated cardiac amyloid, systemic senile amyloidoses, AIAPP or amylin insulinoma, atrial naturetic factor (isolated atrial amyloid), procalc
• the present method provides a means of evaluating success of anti-amyloid therapies. In some embodiments, the present method provides a means for evaluating clinical success of anti-amyloid therapies. In some embodiments, the method may be used to evaluate clinical success in mildly impaired subjects with few or no clinical symptoms to follow.
• the basic method of determining the efficacy of therapy in the treatment of amyloidosis involves:
• Z is S, NR', O or C(R') 2 , such that when Z is C(R') 2 , the tautomeric form of the heterocyclic ring may form an indole:
• R' is H or a lower alkyl group
• Y is NR 1 R 2 , OR 2 , or SR 2 ,
• R pn represents an unsubstituted or substituted phenyl group with the phenyl substituents being chosen from any of the non-phenyl substituents defined for R ⁇ R 10 and wherein R' is H or a lower alkyl group
• M is selected from the group consisting of Tc and Re; and radiolabeled derivatives and pharmaceutically acceptable salts thereof, where at least one of the substituent moieties comprises a detectable label;
• the detectable label includes any atom or moiety which can be detected using an imaging technique known to those skilled in the art.
• the detectable label is a radiolabel.
• the detectable label is a radiolabel.
• amyloid probe of the present invention is any compound of formula (I), described above.
• amyloid probe is a compound of formula (II)
• R 1 is hydrogen, -OH, -NO 2 , -CN, -COOR, -OCH 2 OR, C 1 -C 6 alkyl, C 2 -C 6 alkenyl, C 2 -C 6 alkynyl, C 1 -C 6 alkoxy or halo; R is C 1 -C 6 alkyl;
• R 2 is hydrogen or halo
• R 3 is hydrogen, C 1 -C 6 alkyl, C 2 -C 6 alkenyl or C 2 -C 6 alkynyl;
• R 4 is hydrogen, C 1 -C 6 alkyl, C 2 -C 6 alkenyl or C 2 -C 6 alkynyl, wherein the alkyl, alkenyl or alkynyl comprises a radioactive carbon or is substituted with a radioactive halo when R 2 is hydrogen or a non-radioactive halo; provided that when R 1 is hydrogen or -OH, R 2 is hydrogen and R 4 is - 11 CH 3 , then R 3 is C 2 -C 6 alkyl, C 2 -C 6 alkenyl or C 2 -C 6 alkynyl; and further provided that when R 1 is hydrogen, R 2 hydrogen and R 4 is -(CH 2 ) 3 18 F, then R 3 is C 2 -C 6 alkyl, C 2 -C 6 alkenyl or C 2 -C 6 alkynyl, where at least one of the substituent moieties comprises a detectable label.
• R 2 in the compounds of formula (II) contains a radioactive halo.
• Alkyl refers to a saturated straight or branched chain hydrocarbon radical. Examples include without limitation methyl, ethyl, propyl, iso-propyl, butyl, iso- butyl, tert-butyl, n-pentyl and n-hexyl.
• lower alkyl refers to C 1 -C 6 alkyl.
• Alkenyl refers to an unsaturated straight or branched chain hydrocarbon radical comprising at least one carbon to carbon double bond. Examples include without limitation ethenyl, propenyl, iso-propenyl, butenyl, iso-butenyl, fert-butenyl, n-pentenyl and n-hexenyl.
• Alkynyl refers to an unsaturated straight or branched chain hydrocarbon radical comprising at least one carbon to carbon triple bond. Examples include without limitation ethynyl, propynyl, iso-propynyl, butynyl, iso-butynyl, tert-butynyl, pentynyl and hexynyl.
• Alkoxy refers to an alkyl group bonded through an oxygen linkage.
• Halo refers to a fluoro, chloro, bromo or iodo radical.
• Radioactive halo refers to a radioactive halo, i.e. radiofluoro, radiochloro, radiobromo or radioiodo.
• the thioflavin compound of formula (I) is selected from the group consisting of structures 1-45 or a radiolabeled derivative thereof:
• the amyloid probe is ⁇ N-methyl- n C ⁇ 2-[4'- (methylamino)phenyl]6-hydroxybenzothiazole ("[ 11 C]PIB”) or ⁇ N-methyl- 3 H ⁇ 2-[4'- (methylamino)phenyl] 6-hydroxybenzothiazole (“ [ 3 H] PIB”) .
• Effective amount refers to the amount required to produce a desired effect.
• Examples of an “effective amount” include amounts that enable detecting and imaging of amyloid deposit(s) in vivo or in vitro, that yield acceptable toxicity and bioavailability levels for pharmaceutical use, and/or prevent cell degeneration and toxicity associated with fibril formation.
• thioflavin compounds also referred to herein as "thioflavin compounds,” “thioflavin derivatives,” or “amyloid probes,” have each of the following characteristics: (1) specific binding to synthetic A ⁇ in vitro and (2) ability to cross a non-compromised blood brain barrier in vivo.
• the thioflavin compounds and radiolabeled derivatives thereof of formulas (I) and (II) and structures 1-45 cross the blood brain barrier in vivo and bind to A ⁇ deposited in neuritic (but not diffuse) plaques, to A ⁇ deposited in cerebrovascular amyloid, and to the amyloid consisting of the protein deposited in NFT.
• the present compounds are non-quaternary amine derivatives of Thioflavin S and T which are known to stain amyloid in tissue sections and bind to synthetic A ⁇ in vitro. Kelenyi J. Histochem. Cytochem. 15: 172 (1967); Burns et al. J. Path. Bad. 94:337 (1967); Guntern et al.
• the method of this invention determines the presence and location of amyloid deposits in an organ or body area, preferably brain, of a patient.
• the present method comprises administration of a detectable quantity of an amyloid probe of formulas (I) or (II) and structures 1-45.
• the amyloid probe is chosen from structures 1-45, as shown above.
• An amyloid probe may be administered to a patient as a pharmaceutical composition or a pharmaceutically acceptable water-soluble salt thereof.
• “Pharmaceutically acceptable salt” refers to an acid or base salt of the inventive compound, which salt possesses the desired pharmacological activity and is neither biologically nor otherwise undesirable.
• the salt can be formed with acids that include without limitation acetate, adipate, alginate, aspartate, benzoate, benzenesulfonate, bisulfate butyrate, citrate, camphorate, camphorsulfonate, cyclopentanepropionate, digluconate, dodecylsulfate, ethanesulfonate, fumarate, glucoheptanoate, glycerophosphate, hemisulfate, heptanoate, hexanoate, hydrochloride hydrobromide, hydroiodide, 2-hydroxyethane-sulfonate, lactate, maleate, methanesulfonate, 2-naphthalenesulfonate, nicotinate, oxalate, thi
• Examples of a base salt include without limitation ammonium salts, alkali metal salts such as sodium and potassium salts, alkaline earth metal salts such as calcium and magnesium salts, salts with organic bases such as dicyclohexylamine salts, N-methyl-D-glucamine, and salts with amino acids such as arginine and lysine.
• the basic nitrogen-containing groups can be quarternized with agents including lower alkyl halides such as methyl, ethyl, propyl and butyl chlorides, bromides and iodides; dialkyl sulfates such as dimethyl, diethyl, dibutyl and diamyl sulfates; long chain halides such as decyl, lauryl, myristyl and stearyl chlorides, bromides and iodides; and aralkyl halides such as phenethyl bromides.
• lower alkyl halides such as methyl, ethyl, propyl and butyl chlorides, bromides and iodides
• dialkyl sulfates such as dimethyl, diethyl, dibutyl and diamyl sulfates
• long chain halides such as decyl, lauryl, myristyl and stearyl chlorides, bromides and
• the dosage of the detectably labeled thioflavin derivative will vary depending on considerations such as age, condition, sex, and extent of disease in the patient, contraindications, if any, concomitant therapies and other variables, to be adjusted by a physician skilled in the art. Dosage can vary from 0.001 ⁇ g/kg to 10 ⁇ g/kg, preferably 0.01 ⁇ g/kg to 1.0 ⁇ g/kg.
• Administration to the subject may be local or systemic and accomplished intravenously, intraarterially, intrathecally (via the spinal fluid) or the like. Administration may also be intradermal or intracavitary, depending upon the body site under examination. After a sufficient time has elapsed for the compound to bind with the amyloid, for example 30 minutes to 48 hours, the area of the subject under investigation is examined by routine imaging techniques such as MRS/MRI, SPECT, planar scintillation imaging, PET, and any emerging imaging techniques, as well. The exact protocol will necessarily vary depending upon factors specific to the patient, as noted above, and depending upon the body site under examination, method of administration and type of label used; the determination of specific procedures would be routine to the skilled artisan.
• the amount (total or specific binding) of the bound radioactively labeled thioflavin derivative or analogue of the present invention is measured and compared (as a ratio) with the amount of labeled thioflavin derivative bound to the cerebellum of the patient. This ratio is then compared to the same ratio in age-matched normal brain.
• amyloid probes of the present invention are advantageously administered in the form of injectable compositions, but may also be formulated into well known drug delivery systems (e.g., oral, rectal, parenteral (intravenous, intramuscular, or subcutaneous), intracisternal, intravaginal, intraperitoneal, local (powders, ointments or drops), or as a buccal or nasal spray).
• a typical composition for such purpose comprises a pharmaceutically acceptable carrier.
• the composition may contain about 10 mg of human serum albumin and from about 0.5 to 500 micrograms of the labeled thioflavin derivative per milliliter of phosphate buffer containing NaCl.
• compositions include aqueous solutions, non-toxic excipients, including salts, preservatives, buffers and the like, as described, for instance, in REMINGTON'S PHARMACEUTICAL SCIENCES, 15th Ed. Easton: Mack Publishing Co. pp. 1405-1412 and 1461-1487 (1975) and THE NATIONAL FORMULARY XIV., 14th Ed. Washington: American Pharmaceutical Association (1975), the contents of which are hereby incorporated by reference.
• amyloid probes of the present invention are those that, in addition to specifically binding amyloid in vivo and capable of crossing the blood brain barrier, are also non-toxic at appropriate dosage levels and have a satisfactory duration of effect.
• a pharmaceutical composition comprising an amyloid probe of formula (I) or formula (II) or one of the structures 1-45, is administered to subjects in whom amyloid or amyloid fibril formation are anticipated, e.g., patients clinically diagnosed with Alzheimer's disease or another disease associated with amyloid deposition.
• non-aqueous solvents examples include propylene glycol, polyethylene glycol, vegetable oil and injectable organic esters such as ethyl oleate.
• Aqueous carriers include water, alcoholic/aqueous solutions, saline solutions, parenteral vehicles such as sodium chloride, Ringer's dextrose, etc.
• Intravenous vehicles include fluid and nutrient replenishers.
• Preservatives include antimicrobial, anti-oxidants, chelating agents and inert gases. The pH and exact concentration of the various components the pharmaceutical composition are adjusted according to routine skills in the art. See, Goodman and Gilman's THE PHARMACOLOGICAL BASIS FOR THERAPEUTICS (7th Ed.).
• the invention employs amyloid probes which, in conjunction with non ⁇ invasive neuroimaging techniques such as magnetic resonance spectroscopy (MRS) or imaging (MRI), or gamma imaging such as positron emission tomography (PET) or single-photon emission computed tomography (SPECT), are used to quantify amyloid deposition in vivo.
• the method involves imaging a patient to establish a baseline of amyloid deposition.
• baseline refers to the amount and distribution of a patient's amyloid deposition prior to initiation of the anti-amyloid therapy.
• the method further involves at least one imaging session of a patient following administration of an anti-amyloid therapy.
• the present method may involve imaging a patient before and after treatment with at least one anti-amyloid agent.
• Imaging may be performed at any time during the treatment.
• the term "in vivo imaging” refers to any method which permits the detection of a labeled thioflavin derivative of formulas (I) or (II) or one of structures 1-45.
• the radiation emitted from the organ or area being examined is measured and expressed either as total binding or as a ratio in which total binding in one tissue is normalized to (for example, divided by) the total binding in another tissue of the same subject during the same in vivo imaging procedure.
• Total binding in vivo is defined as the entire signal detected in a tissue by an in vivo imaging technique without the need for correction by a second injection of an identical quantity of labeled compound along with a large excess of unlabeled, but otherwise chemically identical compound.
• a “subject” is a mammal, preferably a human, and most preferably a human suspected of having a disease associated with amyloid deposition, such as AD and/or dementia.
• the term “subject” and “patient” are used interchangeably herein.
• the type of detection instrument available is a
• radioactive isotopes and F are particularly suitable for in vivo imaging in the methods of the present invention.
• the type of instrument used will guide the selection of the radionuclide or stable isotope.
• the radionuclide chosen must have a type of decay detectable by a given type of instrument.
• Another consideration relates to the half-life of the radionuclide. The half-life should be long enough so that it is still detectable at the time of maximum uptake by the target, but short enough so that the host does not sustain deleterious radiation.
• the radiolabeled compounds of the invention can be detected using gamma imaging wherein emitted gamma irradiation of the appropriate wavelength is detected.
• Methods of gamma imaging include, but are not limited to, SPECT and PET.
• the chosen radiolabel will lack a particulate emission, but will produce a large number of photons in a 140-200 keV range.
• the radiolabel will be a positron-emitting radionuclide such as 18 F which will annihilate to form two 511 keV gamma rays which will be detected by the PET camera.
• amyloid binding compounds/probes which are useful for in vivo imaging and quantification of amyloid deposition, are administered to a patient.
• thioflavin derivatives may be labeled with 18 F or 13 C for MRS/MRI by general organic chemistry techniques known to the art. See, e.g., March, J. ADVANCED ORGANIC CHEMISTRY: REACTIONS, MECHANISMS, AND STRUCTURE (3rd Edition, 1985), the contents of which are hereby incorporated by reference.
• the thioflavin derivatives also may be radiolabeled with 18 F, 11 C, 75 Br, or 76 Br for PET by techniques well known in the art and are described by Fowler, J. and Wolf, A. in POSITRON EMISSION TOMOGRAPHY AND AUTORADIOGRAPHY (Phelps, M., Mazziota, J., and Schelbert, H. eds.) 391-450 (Raven Press, NY 1986) the contents of which are hereby incorporated by reference.
• the thioflavin derivatives also may be radiolabeled with 123 I for SPECT by any of several techniques known to the art. See, e.g.,
• the thioflavin derivatives may be labeled with any suitable radioactive iodine isotope, such as, but not limited to 131 I, 125 I, or 123 I, by iodination of a diazotized amino derivative directly via a diazonium iodide, see Greenbaum, F. Am. J. Pharm.
• a stable triazene or tri-alkyl tin derivative of thioflavin or its analogues is reacted with a halogenating agent containing 131 1, 125 1, 123 I, 76 Br, 75 Br, 18 F or 19 F.
• a halogenating agent containing 131 1, 125 1, 123 I, 76 Br, 75 Br, 18 F or 19 F.
• the stable tri-alkyl tin derivatives of thioflavin and its analogues are novel precursors useful for the synthesis of many of the radiolabeled compounds within the present invention.
• these tri-alkyl tin derivatives are one embodiment of this invention.
• the thioflavin derivatives also may be radiolabeled with known metal radiolabels, such as Technetium-99m ( 99m Tc). Modification of the substituents to introduce ligands that bind such metal ions can be effected without undue experimentation by one of ordinary skill in the radiolabeling art.
• the metal radiolabeled thioflavin derivative can then be used to detect amyloid deposits. Preparing radiolabeled derivatives of Tc 99 " 1 is well known in the art.
• the methods of the present invention may use isotopes detectable by nuclear magnetic resonance spectroscopy for purposes of in vivo imaging and spectroscopy.
• Elements particularly useful in magnetic resonance spectroscopy include 18 F and 13 C.
• Suitable radioisotopes for purposes of this invention include beta-emitters, gamma-emitters, positron-emitters, and x-ray emitters. These radioisotopes include 131 1, 123 1, 18 F, 11 C, 75 Br, and 76 Br.
• Suitable stable isotopes for use in Magnetic Resonance Imaging (MRI) or Spectroscopy (MRS), according to this invention include 18 F and 13 C.
• Suitable radioisotopes for in vitro quantification of amyloid in homogenates of biopsy or post-mortem tissue include 125 1, 14 C, and 3 H.
• the preferred radiolabels are 11 C or 18 F for use in PET in vivo imaging, 123 I for use in SPECT imaging, 19 F for MRS/MRI, and 3 H or 14 C for in vitro studies.
• any conventional method for visualizing diagnostic probes can be utilized in accordance with this invention.
• the method involves incubating formalin-fixed tissue with a solution of a thioflavin amyloid binding compound chosen from compounds of formulas (I) and (II) or structures 1-45, described above.
• the solution is 25-100% ethanol, (with the remainder being water) saturated with a thioflavin amyloid binding compound of formulas (I) or (II) or structures 1-45 according to the invention.
• the compound stains or labels the amyloid deposit in the tissue, and the stained or labeled deposit can be detected or visualized by any standard method.
• detection means include microscopic techniques such as bright-field, fluorescence, laser-confocal and cross-polarization microscopy.
• the method of quantifying the amount of amyloid in biopsy tissue involves incubating a labeled derivative of thioflavin according to the present invention, or a water-soluble, non-toxic salt thereof, with homogenate of biopsy or post-mortem tissue.
• the tissue is obtained and homogenized by methods well known in the art.
• the preferred label is a radiolabel, although other labels such as enzymes, chemiluminescent and immunofluorescent compounds are well known to skilled artisans.
• the preferred radiolabel is 125 1, 14 C or 3 H which is contained in a substituent substituted on one of the compounds of formulas (I) or (II) or structures 1-45.
• Tissue containing amyloid deposits will bind to the labeled derivatives of the thioflavin amyloid binding compounds of the present invention.
• the bound tissue is then separated from the unbound tissue by any mechanism known to the skilled artisan, such as filtering.
• the bound tissue can then be quantified through any means known to the skilled artisan.
• the units of tissue-bound radiolabeled thioflavin derivative are then converted to units of micrograms of amyloid per 100 mg of tissue by comparison to a standard curve generated by incubating known amounts of amyloid with the radiolabeled thioflavin derivative.
• the ability of the compound of formulas (I) and (II) or structures 1-45 to specifically bind to amyloid plaques over neurofibrially tangles is particularly true at concentrations less than 10 nM, which includes the in vivo concentration range of PET radiotraces. At these low concentrations, in homogenates of brain tissue which contain only tangles and no plaques, significant binding does not result when compared to control brain tissue containing neither plaques nor tangles. However, incubation of homogenates of brain tissue which contains mainly plaques and some tangles with radiolabeled compounds of Formula (I) or (II) or structures 1-45, results in a significant increase in binding when compared to control tissue without plaques or tangles.
• the present method for determining the efficacy of therapy in the treatment of amyloidosis involves administering to a patient in need thereof a compound of formulas (I) or (II) or structure 1-45 and imaging the patient, and, after said imaging, administering at least one anti-amyloid agent/anti-amyloid therapy said patient.
• the amount administered, the route of administration, and the duration of therapy are determined by one skilled in the art based on age, weight, and condition of the patient. Such determinations are within the purview of the skilled practitioner. Suitable amounts include, but are not limited to, 0.01 to 100 mg/kg.
• Suitable routes of administration include, but are not limited to oral, subcutaneous and intravenous.
• Suitable durations of therapy include, but are not limited to one single dose to four doses per day given indefinitely.
• Suitable times to image include, but are not limited to immediately after the first dose to ten years after the most recent dose. Preferred times to image would be between 7 days and 6 months after the most recent dose.
• An "Anti-amyloid agent” or an “anti-amyloid therapy” is any agent or combination of agents that treat or prevent amyloidosis.
• amyloid deposition examples include Alzheimer's Disease, Down's Syndrome, Type 2 diabetes mellitus, hereditary cerebral hemorrhage amyloidosis (Dutch), amyloid A (reactive), secondary amyloidosis, MCI, familial mediterranean fever, familial amyloid nephropathy with urticaria and deafness (Muckle-wells Syndrome), amyloid lambda L-chain or amyloid kappa L-chain (idiopathic, myeloma or macroglobulinemia-associated) A beta 2M (chronic hemodialysis), ATTR (familial amyloid polyneuropathy (Portuguese, Japanese, Swedish)), familial amyloid cardiomyopathy (Danish), isolated cardiac amyloid, systemic senile amyloidoses, AIAPP or amylin insulinoma, atrial naturetic factor
• the invention encompasses diseases associated with amyloid plaque deposition.
• the disease associated with amyloid deposition is associated with amyloid plaque deposition.
• the disease associated with amyloid deposition is associated with amyloid plaque deposition.
• Treatment includes treating and/or preventing disease.
• Treatment refers to:
• treating does not necessarily mean total cure. Any alleviation of any undesired symptom or pathological effect of the disease to any extent or the slowing down of the progress of the disease can be considered treatment. Furthermore, treatment may include acts which may worsen the patient's overall feeling of well being or appearance. For example, the administration of chemotherapy in cancer patients which may leave the patients feeling "sicker" is still considered treatment.
• the term "preventing” refers to decreasing the probability that an organism contracts or develops a disease associated with amyloid deposition.
• the term “preventing” preferably refers to reducing the percentage of individuals who develop the disease relative to a control group that does not undergo administration of an anti- amyloid agent.
• the present invention is directed to amyloid imaging serving as a surrogate marker of efficacy for anti-amyloid therapy. Administration of an amyloid probe to establish a baseline of amyloid deposition and subsequent imaging of a patient both before and after treatment of the patient with an anti-amyloid agent allows for determination of the efficacy of the anti-amyloid therapy.
• the present method can be used to determine the efficacy of any anti-amyloid treatment because an amyloid probe can be administered, and the patient can be imaged, before and after any anti- amyloid therapy.
• the present method contemplates determining anti-amyloid therapies which are ineffective for treating diseases associated with amyloid deposition, as well as anti-amyloid therapies which are effective for treating diseases associated with amyloid deposition.
• a person of ordinary skill in the art can determine the conditions and dosing of the anti-amyloid therapy according to appropriate protocols. Therefore, the present invention contemplates determining the efficacy of anti-amyloid therapies that are now known, as well as therapies that are yet to be discovered. Exemplary non-limiting anti-amyloid therapies are described below.
• the efficacy of acetylcholinesterase inhibitors in the treatment of amyloidosis is determined by the present method.
• Acetylcholinesterase therapy is based on studies of degeneration patterns in AD which identified substantial decreases among groups of neurons in the basal forebrain. These cells all used the transmitter acetylcholine, and their loss meant that less acetylcholine was being released at their former terminals in the cortex.
• drugs such as tacrine, donepezil, rivastigmine and galantamine have been developed based on these findings, and are hypothesized to work by inhibiting the enzyme acetylcholinesterase (Ingram, V., American Scientist, 2003, 91(4):312-321).
• the efficacy of anti-amyloid therapy targeting enzymes responsible for formation of noxious fragments of amyloid precursor protein (APP) in the treatment of amyloidosis is determined by the present method.
• the noxious fragments of the amyloid precursor protein (APP) is misfolded A ⁇ peptide.
• the overproduction of A ⁇ 1-42 fragment is considered by some scientists to be a root cause of AD.
• the A ⁇ l-42 fragment is formed by cleavage of APP by the ⁇ -secretase enzyme (BACEl) (which produces the amino terminus) and the ⁇ -secretase enzyme (which cleaves the carboxyl terminus of APP). Inhibitors of these secretase enzymes may be used as anti-amyloid therapies (Ingram, V., American Scientist, 2003, 91(4):312-321).
• the efficacy of immunotherapeutic strategies in the treatment of amyloidosis can be determined by the present method.
• Immunotherapy works by using the patient's immune system to locate and destroy amyloid plaques and many immunotherapy strategies are being actively pursued by scientists.
• the immunotherapeutic strategies can be either passive or active.
• active immunotherapy a patient may receive an injection or nasal-spray application of the A ⁇ peptide, leading to an anti-amyloid immune response.
• Passive immunotherapy might involve bypassing the beta amyloid protein, using instead antiserum that has already been produced in response to beta amyloid.
• AN- 1792 is a preparation of preaggregated synthetic amyloid-beta (A ⁇ ; 1-42 length) along with QS-21 adjuvant (Hock, C. et al, 2003, Neuron, 38:547-554). Approximately 300 AD patients have been treated with this preparation prior to suspension of the clinical trial due to side effects (Birmingham, K. and Frantz, S., 2002, Nature Medicine, 8:199-200).
• the efficacy of neuroprotective strategies in the treatment of amyloidosis is determined by the present method. For example, many clinicians recommend that patients take high doses (1000-2000 IU/day) of vitamin E. Other types of neuroprotective strategies that have been suggested for the treatment of amyloidosis are high doses of vitamin C, calcium channel modulators, free-radical scavengers, and metal ion chelators (Selkoe, et al., Annu. Rev. Pharmacol. Toxicol., 2003, 43:545-84). In some embodiments, the efficacy of anti-inflammatory drugs (NS AIDs) strategies in the treatment of amyloidosis is determined by the present method.
• NS AIDs anti-inflammatory drugs
• Treatments involving NSAIDs are based on evidence that a cellular inflammatory response in the cortex is elicited by the progressive accumulation of A ⁇ peptide.
• exemplary anti-inflammatory drugs are prednisone, nonspecific cyclooxygenase inhibitors, and cyclooxygenase-2 inhibitors. (Clark, M., et al., Annals of Internal Medicine, 2003, 138(5):400-410; and Hardy, John, Annu. Rev. Med., 2004, 55:15- 25).
• the efficacy of cholesterol-lowering therapies including, but not limited to, the 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors (statins) is determined by the present method.
• Treatments involving cholesterol-lowering drugs are based on epidemiological evidence that patients treated with statins have a lower incidence of AD and that statins can alter the metabolism of A ⁇ to decrease A ⁇ levels (Wolozin,B (2002) Cholesterol and Alzheimer's disease. Biochemical Society Transactions. 30:525-529).
• Exemplary cholesterol-lowering statin drugs include lovastatin, pravastatin, rosuvastatin, fluvastatin, atorvastatin and simvastatin.
• Other cholesterol-lowering drugs include niacin, cholestyramine, fenofibrate, colesevelam and ezetimibe.
• the efficacy of small molecules that eliminate the neurotoxicity of the aggregated A ⁇ 1 -42 in the treatment of amyloidosis is determined by the present method.
• a drug preferably administered early in disease progression, would "detoxify" the gradually accumulating A ⁇ peptide before any permanent damage is inflicted on the neurons.
• the efficacy of "decoy peptides" in the treatment of amyloidosis is determined by the present method. Decoy peptides are small molecules that bind to the aggregating A ⁇ 1-42 peptide and force it to assume a nontoxic structure.
• Exemplary decoy peptides are small peptides (5, 6 or 9 amino acids long), selected from large libraries of protein fragments by their ability to form a tight association with tagged A ⁇ 1 -42. (Clark, M., et al, Annals of Internal Medicine, 2003, 138(5):400-410).
• the efficacy of cholesterol homeostasis modulation in the treatment of amyloidosis is determined by the present method.
• Chronic use of cholesterol-lowering drugs has recently been associated with a lower incidence of AD.
• high-cholesterol diets have been shown to increase A ⁇ pathology in animals, and cholesterol-lowering drugs have been shown to reduce pathology in APP transgenic mice.
• Clinical trials are underway to study the effect of cholesterol homeostasis modulation in the treatment of AD. (Hardy, John, Annu. Rev. Med., 2004, 55:15-25)
• m266 deMattos,RB, Bales,KR, Cummins,DJ, DodartJC, Paul,SM, Holtzman,DM (2001) "Peripheral anti-A beta antibody alters CNS and plasma A beta clearance and decreases brain A beta burden in a mouse model of Alzheimer's disease.” Proc.Natl.Acad.Sci.USA 98:8850-8855) or molecules other than antibodies (Matsuoka,Y, Saito,M, LaFrancois,J, Saito,M, Gaynor,K, Olm, V, Wang,L, Casey,E, Lu 5 Y, Shiratori,C, Lemere,C, Duff,K (2001) "Novel therapeutic approach for the treatment of Alzheimer's disease by peripheral administration of agents with an affinity to beta-amyloid.” Journal of Neuroscience.
• peripheral sink agents are believed to lower brain amyloid by binding to A ⁇ peptides in the blood, thereby creating a "peripheral sink” and shifting the equilibrium of A ⁇ from the brain to the blood, where it can be cleared from the body.
• peripheral sink agents Such agents are referred to herein as “peripheral sink agents.”
• the present method for determining the efficacy of therapy in the treatment of amyloidosis involves administering to a patient in need thereof a compound of formulas (I) or (II) or structure 1-45 and imaging the patient. After said imaging, at least one anti-amyloid agent is administered to said patient. Then, an effective amount of a compound of formulas (I) or (II) or structure 1-45 is administered to the patient and the patient is imaged again. Finally, baseline levels of amyloid deposition in the patient before treatment with the anti-amyloid agent are compared with levels of amyloid deposition in the patient following treatment with the anti-amyloid agent. Such a comparison is within the perview of a skilled practitioner.
• the levels of amyloid deposition in the patient before treatment with the anti-amyloid agent will be higher than the levels of amyloid deposition in the patient following treatment with the anti-amyloid agent.
• AN- 1792 is a preparation of preaggregated synthetic amyloid- beta (A ⁇ ; 1-42 length) along with QS-21 adjuvant. Approximately 300 AD patients have been treated with this preparation prior to suspension of the clinical trial due to side effects (Birmingham, K. and Frantz, S., 2002, Nature Medicine, 8:199-200).
• TPIR tissue amyloid plaque immunoreactivity
• benzothiazole amyloid imaging probes which are useful as PET tracers, such as [ 11 C]PIB, could detect changes in amyloid deposition in AD brain induced by AN- 1792 treatment and by other therapies that have a significant effect on brain amyloid deposition in AD.
• R 1 is hydrogen, -OH, -NO 2 , -CN, -COOR, -OCH 2 OR, C 1 -C 6 alkyl, C 2 -C 6 alkenyl, C 2 -C 6 alkynyl, C 1 -C 6 alkoxy or halo, wherein one or more of the atoms of R 1 may be a radiolabeled atom;
• R is C 1 -C 6 alkyl, wherein one or more of the carbon atoms may be a radiolabeled atom; is hydrolysed by one of the following two procedures: Preparation of 2-aminothiophenol via hydrolysis:
• the 6-substituted 2-aminobenzothiazole (172 mmol) is suspended in 50% KOH (180 g KOH dissolved in 180 niL water) and ethylene glycol (40 niL). The suspension is heated to reflux for 48 hours. Upon cooling to room temperature, toluene (300 niL) is added and the reaction mixture is neutralized with acetic acid (180 niL). The organic layer is separated and the aqueous layer is extracted with another 200 mL of toluene. The toluene layers are combined and washed with water and dried over MgSO 4 . Evaporation of the solvent gives the desired product.
• R 2 is hydrogen
• R 3 and R 4 are independently hydrogen, C 1 -C 6 alkyl, C 2 -C 6 alkenyl or C 2 -C 6 alkynyl by the following methodology:
• the R 2 hydrogen can be substituted with either a non-radioactive halo or a radioactive halo by the following reaction: To a solution of 6-substituted 2-(4'-aminophenyl)-benzothiazole (1 mg) in
• acetic acid in a sealed vial 250 ⁇ L acetic acid in a sealed vial is added 40 ⁇ L of chloraniine-T solution (28 mg dissolved in 500 ⁇ L acetic acid) followed by 27 ⁇ L (ca. 5 mCi) of sodium [ 125 I]iodide (specific activity 2,175 Ci/mmol).
• the reaction mixture is stirred at room temperature for 2.5 hours and quenched with saturated sodium hydrogensulfite solution. After dilution with 20 ml of water, the reaction mixture is loaded onto C8 Plus SepPak and eluted with 2 ml methanol.
• protecting groups may need to be employed.
• the 6-hydroxy group is protected as the methanesulfonyl (mesyloxy) derivative.
• methanesulfonyl methanesulfonyl (mesyloxy) derivative.
• 0.5 ml of 1 M NaOH is added to the eluted solution of radioiodinated intermediate.
• the mixture is heated at 50 0 C for 2 hours.
• 500 ⁇ L of 1 M acetic acid the reaction mixture is diluted with 40 mL of water and loaded onto a C8 Plus SepPak.
• the radioiodinated product having a radioactivity of ca. 3 mCi, is eluted off the SepPak with 2 mL of methanol.
• the solution is condensed by a nitrogen stream to 300 ⁇ L and the crude product is purified by HPLC on a Phenomenex ODS column (MeCN/TEA buffer, 35:65, pH 7.5, flow rate 0.5 mL/minute up to 4 minutes, 1.0 mL/minute at 4-6 minutes, and 2.0 mL/minute after 6 minutes, retention time 23.6).
• the collected fractions are loaded onto a C8 Plus SepPak. Elution with 1 mL of ethanol gave ca. 1 mCi of the final radioiodinated product.
• R 3 and R 4 can be converted to C 1 -C 6 alkyl, C 2 -C 6 alkenyl or C 2 -C 6 alkynyl by reaction with an alkyl, alkenyl or alkynyl halide under the following conditions:
• R 4 is C 1 -C 6 alkyl, C 2 -C 6 alkenyl or C 2 -C 6 alkynyl, wherein the alkyl, alkenyl or alkynyl comprises a radioactive carbon or is substituted with a radioactive halo
• the compound can be synthesized by one of the following sequences:
• Approximately 1 Ci of [ 11 C] carbon dioxide is produced using a CTI/Siemens RDS 112 negative ion cyclotron by irradiation of a nitrogen gas ( 14 N 2 ) target containing 1% oxygen gas with a 40 ⁇ A beam current of 11 MeV protons for 60 minutes.
• [ ⁇ C]Carbon dioxide is converted to [ ⁇ C]methyl iodide by first reacting it with a saturated solution of lithium aluminum hydride in THF followed by the addition of hydriodic acid at reflux temperature to generate [ ⁇ C]methyl iodide.
• the [ n C]methyl iodide is carried in a stream of nitrogen gas to a reaction vial containing the precursor for radiolabeling.
• the precursor, 6-substituted 2-(4'-aminophenyl)- benzothiazole (-3.7 ⁇ moles), is dissolved in 400 ⁇ L of DMSO.
• Dry KOH (10 mg) is added, and the 3 mL V-vial is vortexed for 5 minutes.
• No-carrier-added [ n C]methyl iodide is bubbled through the solution at 30 niL/minute at room temperature. The reaction is heated for 5 minutes at 95° C using an oil bath.
• the reaction product is purified by semi-preparative HPLC using a Prodigy OD S -Prep column eluted with 60% acetonitrile/40% triethylammonium phosphate buffer pH 7.2 (flow at 5 mL/minute for 0-7 minutes then increased to 15 mL/minute for 7-30 minutes).
• the fraction containing [N-methyl- n C] 6-substituted 2-(4'-methylaminophenyl)- benzothiazole (at about 15 min) is collected and diluted with 50 mL of water and eluted through a Waters C18 SepPak Plus cartridge.
• the C18 SepPak is washed with 10 mL of water, and the product is eluted with 1 mL of ethanol (absolute) into a sterile vial followed by 14 mL of saline.
• the radiochemical yield averages 17% at EOS based on [ n C]methyl iodide, and the specific activity averages about 160 GBq/ ⁇ mol (4.3 Ci/ ⁇ mol) at end of synthesis.
• a cyclotron target containing 0.35 mL of 95% [O- 18] -enriched water is irradiated with 11 MeV protons at 20 ⁇ A of beam current for 60 minutes, and the contents are transferred to a 5 mL reaction vial containing Kryptofix 222 (22.3 mg) and K 2 CO 3 (7.9 mg) in acetonitrile (57 ⁇ L).
• the solution is evaporated to dryness three times at HO 0 C under a stream of argon following the addition of 1 mL aliquots of acetonitrile.
• the product, [F-18] 6-substituted 2-(4'-(3"-fluoropropylamino)-phenyl)- benzothiazole is eluted at ⁇ 20 minutes in a volume of about 16 mL.
• the fraction containing [F-18] 6-substituted 2-(4'-(3"-fluoropropylamino)-phenyl)-benzothiazole is diluted with 50 mL of water and eluted through a Waters Cl 8 SepPak Plus cartridge.
• the SepPak cartridge is then washed with 10 mL of water, and the product is eluted using 1 mL of ethanol (absol.) into a sterile vial.
• the solution is diluted with 10 mL of sterile normal saline for intravenous injection into animals.
• the [F-18]6- substituted 2-(4'-(3"-fluoropropylamino)-phenyl)-benzothiazole product is obtained in 2-12% radiochemical yield at the end of the 120 minute radiosynthesis (not decay corrected) with an average specific activity of 1500 Ci/mmol.
• the [ ⁇ C]methyl iodide is carried in stream of nitrogen gas to a reaction vial containing the precursor for radiolabeling.
• the precursor, 6-CH 3 O-BTA-I (1.0 mg, 3.7 ⁇ moles)
• No-carrier-added [ ⁇ C]methyl iodide was bubbled through the solution at 30 mL/minute at room temperature. The reaction was heated for 5 minutes at 95 0 C using an oil bath.
• the reaction product was purified by semi- preparative HPLC using a Prodigy ODS-Prep column eluted with 60% acetonitrile/40% triethylammonium phosphate buffer pH 7.2 (flow at 5 mL/minute for 0-7 minutes then increased to 15 mL/minute for 7-30 minutes).
• the fraction containing [N-Methyl- 11 C]2-(4'-Dimethylaminophenyl)-6-methoxy-benzothiazole (at about 15 minutes) was collected and diluted with 50 mL of water and eluted through a Waters Cl 8 SepPak Plus cartridge.
• the solution was condensed by a nitrogen stream to 300 ⁇ L and the crude product was purified by HPLC on a Phenomenex ODS column (MeCN/TEA buffer, 35:65, pH 7.5, flow rate 0.5 mL/minute up to 4 minutes, 1.0 mL/minute at 4-6 minutes, and 2.0 mL/minute after 6 minutes, retention time 23.6).
• the collected fractions were loaded onto a C8 Plus SepPak. Elution with 1 mL of ethanol gave ca. 1 mCi of the final radioiodinated product.
• Preparation of the 123 I radiolabeled derivatives proceeds similarly to the synthesis outlined above.
• a cyclotron target containing 0.35 mL of 95% [0-18]-enriched water was irradiated with 11 MeV protons at 20 ⁇ A of beam current for 60 minutes, and the contents were transferred to a 5 mL reaction vial containing 2 mg Cs 2 CO 3 in acetonitrile (57 ⁇ L).
• the solution was evaporated to dryness at HO 0 C under a stream of argon three times using 1 mL aliquots of acetonitrile.
• the reduction reaction was allowed to proceed for 10 minutes at room temperature (the crude yield for the reduction step was about 40%).
• To the reaction mixture was added 8 mL of water and 6 mL of diethyl ether, the mixture was shaken and the ether phase separated. The diethyl ether phase was dried under a stream of argon at 12O 0 C.
• To the reaction vial 700 uL of DMSO was added containing 30 micromoles of CH 3 I and 20 mg of dry KOH. The reaction vial was heated at 12O 0 C for 10 minutes.
• a solution of 700 uL of 2:1 MeOH/HCl (concentrated) was added and heated for 15 minutes at 12O 0 C.
• the fraction containing 2-(3- 18 F- fluoro-4-methylamino-phenyl)-benzothiazol-6-ol was diluted with 50 mL of water and eluted through a Waters Cl 8 SepPak Plus cartridge.
• the SepPak cartridge was then washed with 10 mL of water, and the product was eluted using 1 mL of ethanol (absol.) into a sterile vial.
• the solution was diluted with 10 mL of sterile normal saline for intravenous injection into animals.
• the radiochemical purity was >99%, and the chemical purity was >90%.
• the radiochemical identity of 2-(3- 18 F-Fluoro-4-methylamino-phenyl)-benzothiazol-6-ol was confirmed by reverse phase radio-HPLC utilizing a quality control sample of the final radiochemical product co-injected with a authentic (cold) standard.
• Example 4 2-[4-(3- IS F, -Fluoro-propylamino)-phenyl]-benzothiazol-6-olwas synthesized according to Scheme IV.
• a cyclotron target containing 0.35 mL of 95% [O- 18] -enriched water was irradiated with 11 MeV protons at 20 ⁇ A of beam current for 60 minutes, and the contents were transferred to a 5 mL reaction vial containing Kryptofix 222 (22.3 mg) and K 2 CO 3 (7.9 mg) in acetonitrile (57 ⁇ L).
• the solution was evaporated to dryness three times at 11O 0 C under a stream of argon following the addition of 1 mL aliquots of acetonitrile.
• the fraction containing[F-18]6-HO-BTA-N-PrF was diluted with 50 mL of water and eluted through a Waters Cl 8 SepPak Plus cartridge. The SepPak cartridge was then washed with 10 mL of water, and the product was eluted using 1 mL of ethanol (absol.) into a sterile vial. The solution was diluted with 10 mL of sterile normal saline for intravenous injection into animals.
• radiochemical and chemical purities of [F-18]6-HO-BTA-N-PrF were assessed by radio-HPLC with UV detection at 350 nm using a Phenomenex Prodigy ODS(3) C 18 column (5 ⁇ m, 250 x 4.6 mm) eluted with 40% acetonitrile/ 60% 60 mM triethylamine-phosphate buffer (v/v) pH 7.2.
• the radiochemical purity was >99%, and the chemical purity was >90%.
• the radiochemical identity of [F-18]6-HO-BTA-N-PrF was confirmed by reverse phase radio-HPLC utilizing a quality control sample of the final radiochemical product co-injected with a authentic (cold) standard.
• p-Anisidine (1.0 g, 8.1 mmol) was dissolved in anhydrous pyridine (15 ml), 4- nitrobenzoyl chloride (1.5 g, 8.1 mmol) was added. The reaction mixture was allowed to stand at room temperature for 16 hrs. The reaction mixture was poured into water and the precipitate was collected with filtrate under vacuum pressure and washed with 5% sodium bicarbonate(2 x 10 ml). The product was used in the next step without further purification.
• the reaction mixture was loaded onto C8 Plus SepPak and eluted with 2 ml methanol.
• 0.5 ml of 1 M NaOH was added to the eluted solution of radioiodinated intermediate.
• the mixture was heated at 50 0 C for 2 hours.
• 500 ⁇ L of 1 M acetic acid the reaction mixture was diluted with 40 mL of water and loaded onto a C8 Plus SepPak.
• the radioiodinated product having a radioactivity of ca. 3 mCi, was eluted off the SepPak with 2 mL of methanol.
• the benzothiazole amyloid-imaging PET tracer ⁇ N-methyl- ⁇ C ⁇ 2-[4'- (methylamino)phenyl]6-hydroxybenzothiazole (“[ 11 C]PIB") shows a clear difference in retention between AD patients and control subjects. This [ 11 C]PIB retention follows the known topography of amyloid deposition in AD brain (Klunk et al. 2004, Ann. Neurol., 55(3):306-19).
• PIB Binding provides evidence of decreased amyloid load in AN- 1792-treated cases.

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