WO2023097266A1

WO2023097266A1 - Hdac inhibitors for use in the treatment of substance use disorders

Info

Publication number: WO2023097266A1
Application number: PCT/US2022/080417
Authority: WO
Inventors: Venetia ZACHARIOU; Kerri D. PRYCE
Original assignee: Icahn School Of Medicine At Mount Sinai
Priority date: 2021-11-24
Filing date: 2022-11-23
Publication date: 2023-06-01

Abstract

Provided herein are compounds, pharmaceutical compositions comprising such compounds, and methods of using such compounds to treat or prevent diseases or disorders associated with HDAC activity, particularly diseases or disorders that involve activity of HDAC1 and/or HDAC2.

Description

HDAC INHIBITORS FOR USE IN THE TREATMENT OF SUBSTANCE USE DISORDERS RELATED APPLICATIONS [0001] This application claims the benefit and priority under 35 U.S.C. § 119(e) of the filing date of United States Provisional Patent Application Serial Number 63/283180, filed November 24, 2021. The entire contents of the aforementioned application are hereby incorporated by reference. GOVERNMENT SUPPORT [0002] This invention was made with government support under NS086444 awarded by National Institute of Neurological Disorders and Stroke. The government has certain rights in the invention. REFERENCE TO AN ELECTRONIC SEQUENCE LISTING [0003] The contents of the electronic sequence listing (I052670014WO00-SEQ-PRW.xml; Size: 39,802 bytes; and Date of Creation: November 21, 2022) are herein incorporated by reference in their entirety. BACKGROUND [0004] Substance use disorder or addiction is defined as the repeated use of a substance despite experiencing harmful effects. Substance addiction is a highly prevalent public health problem with significant social, medical, and economic burdens. In 2017, 19.7 million Americans (aged 12 and above) struggled with a substance use disorder, with those struggling with an alcohol, drugs, or a dual alcohol and drug use disorder accounting for 74, 38.5, and 12.5% of this population respectively. The socio-economic burden of addiction results from loss of productivity or unemployability, physical and mental health impairment, transmission of infectious diseases (for example, through needle sharing), increase in crime and violence, child abuse and neglect, and excessive utilization of health care. Substance addiction costs the US more than $740 billion annually in lost workplace productivity, healthcare costs and crime-related costs. [0005] The development of physical dependence and addiction disorders due to misuse of opioid analgesics is a major concern with pain therapeutics. Opioid use disorder (OUD), for example, is a chronic lifelong disorder with serious potential consequences including disability, relapses, and death. [0006] Histones are highly alkaline proteins found in eukaryotic cell nuclei. Histone deacetylases (HDACs) are enzymes that remove the acetyl group from an ε-N-acetyl lysine amino acid on a histone. HDAC1 has been shown previously to be a top regulator for several genes implicated in drug dependence, addiction, and pain (Nat. Neurosci. 2013, 16, 434-440). It is therefore hypothesized that inhibition of HDAC1 may alleviate behavioral and emotional abnormalities associated with substance use disorder and withdrawal. [0007] The chronic nature of addiction and the high relapse rates are a considerable challenge for the treatment of substance use disorder. As such, there is clear need for the development of fast acting, more potent therapies with fewer side effects to treat addiction and relapse and to help reduce the individual and public health problems associated with addictive disorders. SUMMARY [0008] Provided herein are methods of treating diseases or disorders associated with HDAC activity, particularly diseases or disorders that involve any type of substance use disorder and/or withdrawal symptom. As such, provided herein is a method of treating a substance use disorder in a subject in need thereof, comprising administering to the subject a therapeutically effective amount of a histone deacetylase 1/2 (HDAC1/2) inhibitor. [0009] Aspects of the disclosure relate to a method of treating a substance use disorder in a subject in need thereof, comprising administering to the subject a therapeutically effective amount of a histone deacetylase 1/2 (HDAC1/2) inhibitor. [0010] In some embodiments, the histone deacetylase 1/2 (HDAC1/2) inhibitor comprises a compound of Formula I:

I, [0011] or a pharmaceutically acceptable salt thereof, wherein R¹ is aryl or heteroaryl; R² is H, C₁-C₆-alkyl, or C₁-C₆-alkyl-N(R^a)2; R³ is H, C₁-C₆-alkyl, C₁-C₆-alkyl-N(R^a)2, or C(O)R^b; or R² and R³, together with the N atom to which they are attached, optionally form a 5 or 6 membered heterocycloalkyl ring, wherein the heterocycloalkyl ring optionally contains a -N(R^c)- moiety and wherein the heterocycloalkyl ring optionally contains a -C(O)- moiety; each R^a is independently H or C₁-C₆-alkyl; R^b is C₁-C₆-alkyl, C₁-C₆-alkyl-N(R^d)2, or a 5 or 6 membered heterocycloalkyl, wherein the heterocycloalkyl is optionally substituted by C₁-C₆-alkyl; R^c is H or C₁-C₆-alkyl; and each R^d is independently H or C₁-C₆-alkyl. [0012] In some embodiments, the R¹ is phenyl, thiophenyl, or pyridinyl. [0013] In some embodiments, the R¹ is phenyl. [0014] In some embodiments, R² is H or C₁-C₆-alkyl; R³ is C₁-C₆-alkyl-N(R^a)2 or C(O)R^b; or R² and R³, together with the N atom to which they are attached, optionally form a 5 or 6 membered heterocycloalkyl ring, wherein the heterocycloalkyl ring optionally contains a -C(O)- moiety and wherein the heterocycloalkyl ring optionally contains a -N(R^c)- moiety. [0015] In some embodiments, R² and R³, together with the N atom to which they are attached, form piperadine, piperazine, or piperidinone. [0016] Aspects of the disclosure relate to a method of treating a substance use disorder in a subject in need thereof, comprising administering to the subject a therapeutically effective amount of a histone deacetylase 1/2 (HDAC1/2) inhibitor of Formula II:

II, [0017] or a pharmaceutically acceptable salt thereof, wherein R¹ is aryl or heteroaryl; and R^c is H or C_1-C₆-alkyl. [0018] In some embodiments, the R^c is H. [0019] Aspects of the disclosure relate to a method of treating a substance use disorder in a subject in need thereof, comprising administering to the subject a therapeutically effective amount of a histone deacetylase 1/2 (HDAC1/2) inhibitor of Compound A.

Compound A; [0020] or a pharmaceutically acceptable salt thereof. [0021] In some embodiments, the disclosure relates to a method of treating a substance use disorder in a subject in need thereof, wherein the subject is addicted to one or more substances selected from the group consisting of alcohol, an opioid, an opiate, and cocaine. [0022] In some embodiments, the disclosure relates to a method of treating a substance use disorder in a subject in need thereof, wherein the subject is addicted to alcohol. [0023] In some embodiments, the disclosure relates to a method of treating a substance use disorder in a subject in need thereof, wherein the subject is addicted to an opioid. [0024] In some embodiments, the disclosure relates to a method of treating a substance use disorder in a subject in need thereof, wherein the subject is addicted to an opiate. [0025] In some embodiments, the disclosure relates to a method of treating a substance use disorder in a subject in need thereof, wherein the subject is addicted to cocaine. [0026] In some embodiments, the opioid is selected from the group consisting of oxycodone, hydrocodone, morphine, oxymorphone, fentanyl, codeine, and tramadol. [0027] In some embodiments, the opioid is oxycodone, morphine, or fentanyl. [0028] In some embodiments, the opioid is oxycodone. [0029] In some embodiments, the method comprises reducing one or more symptoms of a substance use disorder or withdrawal. [0030] In some embodiments, the disclosure relates to a method of treating a substance use disorder in a subject in need thereof, wherein the substance use disorder or withdrawal symptom is selected from the group consisting of mechanical hypersensitivity, hyperalgesia, peripheral nerve damage, anxiety, depression, avolition, and photophobia. [0031] In some embodiments, the mechanical hypersensitivity is mechanical allodynia. [0032] In some embodiments, the substance use disorder or withdrawal symptom is hyperalgesia. [0033] In some embodiments the hyperalgesia is thermal hyperalgesia. BRIEF DESCRIPTION OF DRAWINGS [0034] FIGs.1A-1E illustrates that chronic oxycodone exposure and spontaneous oxycodone withdrawal produce weight loss and sensory deficits in long-term SNI and pain-free mice. [0035] FIGs. 2A-2K illustrates that oxycodone withdrawal alters emotional and social behaviors. [0036] FIGs.3A-3J. illustrates that oxycodone withdrawal alters broad transcriptome patterns in brain reward regions of chronic neuropathic pain and pain-free mice [0037] FIGs. 4A-4R shows predicted biological processes and transcriptional regulators altered by oxycodone withdrawal with chronic neuropathic pain and pain-free states. [0038] FIGs.5A-5E shows transcriptomic effects of oxycodone withdrawal are differentially expressed across reward-related brain regions with chronic SNI and Sham states. [0039] FIGs 6A-6C illustrates the fold change of mRNA in NAc, mPFC, and VTA tissue in the following groups: sham-saline, sham-oxy vs sham saline, SNI-Oxy vs sham-saline. [0040] FIGs. 7A-7E illustrates that pharmacological inhibition of HDAC1/2 using RBC1HI ameliorates sensory hypersensitivity signs of opioid withdrawal. [0041] FIGs. 8A-8F illustrates that RBC1HI treatment reverses affective symptoms of oxycodone withdrawal. [0042] FIGs. 9A-9D illustrates results from assays used to quantify effect of oxycodone withdrawal produces deficits in social and emotional behavior [0043] FIGs.10A-10F illustrates results from pathway analysis highlighting the effect of pain across the NAc, mPFC and VTA. [0044] FIGs. 11A-11C impact of RBC1HI treatment on deficits in sociability and social novelty recognition in male groups of mice. [0045] FIGs. 12A-12B illustrates the provides information on the pharmacokinetic profiling of Compound A.. [0046] FIGs. 13A-13E illustrates that chronic oxycodone exposure and spontaneous oxycodone withdrawal produce weight loss and sensory deficits in long-term SNI and pain- free mice. [0047] FIGs. 14A-14L illustrates that oxycodone withdrawal alters emotional and social behaviors. [0048] FIGs. 15A-15J illustrates that oxycodone withdrawal alters broad transcriptome patterns in brain reward regions of chronic neuropathic pain and pain-free mice [0049] FIGs. 16A-16I shows predicted biological processes and transcriptional regulators altered by oxycodone withdrawal with chronic neuropathic pain and pain-free states. [0050] FIGs. 17A-17F shows transcriptomic effects of oxycodone withdrawal are differentially expressed across reward-related brain regions with chronic SNI and Sham states. [0051] FIGs.18A-18J illustrates that pharmacological inhibition of HDAC1/2 using RBC1HI ameliorates sensory hypersensitivity signs of opioid withdrawal. [0052] FIGs. 19A-19F illustrates that RBC1HI treatment reverses affective symptoms of oxycodone withdrawal. [0053] FIGs. 20A-20C illustrates results from assays used to quantify effect of oxycodone withdrawal produces deficits in social and emotional behavior [0054] FIGs.21A-21F illustrates results from pathway analysis highlighting the effect of pain across the NAc, mPFC and VTA. [0055] FIGs. 22A-22F illustrates validation of protein expression of HDAC1 in cells of the mPFC and NAc and results from RNAscope in situ hybridization to demonstrate co- localization of Hdac1 transcript with common neuronal and microglial transcripts.. [0056] FIGs. 23A-23F illustrates that a novel HDAC1/2 inhibitor reverses mechanical hypersensitivity and thermal hyperalgesia associated with chronic oxycodone exposure. [0057] FIGs. 24A-24C illustrates the impact of RBC1HI treatment on deficits in sociability and social novelty recognition in male groups of mice. DETAILED DESCRIPTION [0058] A biological target of current interest is histone deacetylase (HDAC). Post- translational modification of proteins through acetylation and deacetylation of lysine residues plays a critical role in regulating their cellular functions. HDACs are zinc hydrolases that modulate gene expression through deacetylation of the N-acetyl-lysine residues of histone proteins and other transcriptional regulators (Hassig et al. Curr. Opin. Chem. Biol.1997, 1, 300-308). [0059] Eleven human HDACs, which use Zn as a cofactor, have been identified (Venter et al. Science 2001, 291, 1304-1351) and these members fall into three classes (class I, II, and IV) based on sequence homology to their yeast orthologues (O. Witt et al. Cancer Letters, 2009, 277, 8-21). Class I HDACs include HDAC1, HDAC2, HDAC3, and HDAC8, and are referred to as “classical” HDACs, which implies a catalytic pocket with a Zn²⁺ ion at its base. [0060] Accordingly, provided herein are compounds and methods of using such compounds to treat or prevent diseases or disorders associated with HDAC activity, particularly diseases or disorders that involve any type of HDAC1 and/or HDAC2 activity. Such diseases include, but are not limited to, substance use disorders and symptoms of withdrawal. [0061] Without being limited by theory, it is believed that HDACs (or histone deacetylases) are a group of enzymes that deacetylate histones as well as non-histone proteins. They are known as modulators of gene transcription and are associated with proliferation and differentatin of a variety of cell types and the pathogenesis of various diseases. HDACs are art recognized targets for treating diseases such as, for example, cancer, intersitial fibrosis, autoimmune and inflammatory diseases and metabolic disorders. A review on the use of HDACs for the treatment of disease may be found in Tang et al., “Histone deacetylases as targets for treatment of multiple disease”, Clin Sci (Lond).2013 Jun; 124(11): 651-662, which is herein incorporated by reference in its entirety. [0062] Further, provided herein is a class of HDAC1/2-selective compounds with unique blood brain barrier penetration properties. Thus, the compounds provided herein are particularly suitable for treating central nervous system disorders. These compounds can provide sustained high brain to plasma exposure ratios, which allows for maximum activity in the target tissue and minimizes the toxicity in the periphery known to be associated with HDAC1/2 inhibition. [0063] In some embodiments, the present disclosure relates to the use of HDAC1/2-selective compound for the treatment of a subject with a substance use disorders and symptoms of withdrawal. The HDAC1/2-selective compounds described herein may be used to treat any type of substance use disorder known to one of skill in the art. Non-limiting examples include, for example, opioid use disorder, marijuana use disorder, nicotine use disorder, stimulant use disorder, sedative use disorder, hallucinogen use disorder, alcohol use disorder, gambling disorder, and tabaco use disorder. [0064] In some embodiments, the present disclosure relates to the use of HDAC1/2-selective compounds to alleviate one or more symptoms of withdrawal (e.g., spontaneous withdrawal) in a subject with a substance abuse disorder. The HDAC1/2-selective compounds described herein may be used to treat any type of withdrawal symptom known to one of skill in the art. Non-limiting examples include, for example, whole body symptoms (e.g., pain in the muscles, excessive hunger, fatigue, lethargy, loss of appetite, night sweats, shakiness, clammy skin, craving, feeling cold, or sweating), behavioral symptoms (e.g., agitation, crying, excitability, irritability, restlessness, or self-harm), psychological symptoms (eg delirium depression, hallucination, paranoia, or severe anxiety), gastrointestinal symptoms (e.g,. gagging, nausea, vomiting, flatulence, or stomach cramps), cognitive symptoms (e.g., disorientation, mental confusion, racing thoughts, or slowness in activity), mood symptoms (e.g., boredom, feeling detached from self, loss of interest or pleasure in activities, or nervousness) sleep symptoms (e.g., insomnia, nightmares, sleepiness, or sleeping difficulty), nasal symptoms (e.g., congestion or runny nose), ocular symptoms (e.g., dilated pupil or watery eyes, in addition to other symptoms such as seizures, sensitivity to pain, slurred speech, teeth chattering, tingling feet, trembling, tremor, or weakness. [0065] Methods of diagnosing a subject with a substance use disorder are known in the art and, in some embodiments, may be found, for example, in the Diagnostic and Statistical Manual of Mental Disorders, 5^th edition (DSM-5) published by the American Psychiatric Association on May 18, 2013 and in Hasin et al., “DSM-5 Criteria for Substance Use Disorders: Recommendations and Rationale” Am. J. Psychiatry.2013 Aug 1; 170(8): 834-851, both of which, are hereby incorporated by reference in their entirety. Without wishing to be bound by theory, according to DSM-5, a substance use disorder involved patterns of symptoms caused by using a substance that an individual continues taking despite its negative effects. The DSM-5 points out 11 criteria that can arise from substance misuse. These criteria fall under four basic categories – impaired control, physical dependence, social problems and risky use. The 11 criteria are: [0066] Criterion 1: Using more of a substance than intended or using it for longer than you’re meant to. [0067] Criterion 2: Trying to cut down or stop using the substance but being unable to. [0068] Criterion 3: Experiencing intense cravings or urges to use the substance. [0069] Criterion 4: Needing more of the substance to get the desired effect — also called tolerance. [0070] Criterion 5: Developing withdrawal symptoms when not using the substance. [0071] Criterion 6: Spending more time getting and using drugs and recovering from substance use. [0072] Criterion 7: Neglecting responsibilities at home, work or school because of substance use. [0073] Criterion 8: Continuing to use even when it causes relationship problems. [0074] Criterion 9: Giving up important or desirable social and recreational activities due to substance use. [0075] Criterion 10: Using substances in risky settings that put you in danger. [0076] Criterion 11: Continuing to use despite the substance causing problems to your physical and mental health. [0077] Those in the art familiar with the DSM-5, will understand that the above recited criteria allow a clinician (e.g., medical doctor, nurse practitioner, physician’s assistant, etc.) to determine the severity of a substance use disorder depending on the number of criteria met. For example, a subject exhibiting any one of the eleven symptoms indicates the subject is at risk of developing a substance use disorder. A subject exhibiting two or three criteria may be diagnosed as having a mild substance use disorder. A subject exhibiting four or five criteria may be diagnosed as having a moderate substance use disorder. A subject exhibiting six or more criteria may be diagnosed as having a severe substance use disorder and an addition to a particular substance. [0078] The use of any one of the HDAC1/2-selective compounds disclosed herein may be used to treat a subject with a substance use disorder regardless of the stage of the disease and/or to alleviate one or more symptoms of withdrawal associated with any stage of disease (e.g., at risk, mild, moderate, or severe). Definitions [0079] Listed below are definitions of various terms used to describe this disclosure. These definitions apply to the terms as they are used throughout this specification and claims, unless otherwise limited in specific instances, either individually or as part of a larger group. [0080] Unless defined otherwise, all technical and scientific terms used herein generally have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. Generally, the nomenclature used herein and the laboratory procedures in cell culture, molecular genetics, organic chemistry, and peptide chemistry are those well-known and commonly employed in the art. [0081] As used herein, the articles “a” and “an” refer to one or to more than one (i.e. to at least one) of the grammatical object of the article. By way of example, “an element” means one element or more than one element. Furthermore, use of the term “including” as well as other forms, such as “include,” “includes,” and “included,” is not limiting. [0082] The number of carbon atoms in an alkyl substituent can be indicated by the prefix “C_x-C_y,” where x is the minimum and y is the maximum number of carbon atoms in the substituent. Likewise, a Cx chain means an alkyl chain containing x carbon atoms. [0083] The term “about” generally indicates a possible variation of no more than 10%, 5%, or 1% of a value. For example, “about 25 mg/kg” will generally indicate, in its broadest sense, a value of 22.5-27.5 mg/kg, i.e., 25 ± 2.5 mg/kg. [0084] The term “therapeutically effective amount” of a compound provided herein means a sufficient amount of the compound so as to decrease the symptoms of a disorder in a subject, delay or minimize the onset of symptoms of a disorder in a subject, or prevent the development of symptoms of a disorder in a subject. As is well understood in the medical arts a therapeutically effective amount of a compound of this disclosure will be at a reasonable benefit/risk ratio applicable to any medical treatment. The exact amount required will vary from subject to subject, depending on the species, age, and general condition of the subject, the severity of the disease, the particular active agent, its mode of administration, and the like. A therapeutically effective amount of a compound means an amount of therapeutic agent, alone or in combination with other therapies, which provides a therapeutic benefit in the treatment of the condition. The term “therapeutically effective amount” can encompass an amount that improves overall therapy, reduces or avoids symptoms, signs, or causes of the condition, and/or enhances the therapeutic efficacy of another therapeutic agent. In certain embodiments, a therapeutically effective amount is an amount sufficient for inhibiting HDAC1/2. In certain embodiments, a therapeutically effective amount is an amount sufficient for treating a substance use disorder and/or withdrawal symptoms. In certain embodiments, a therapeutically effective amount is an amount sufficient for inhibiting HDAC1/2 and treating a substance use disorder and/or withdrawal symptoms. [0085] The term “treating” or “treatment” as used herein comprises relieving, reducing or alleviating at least one symptom in a subject or effecting a delay of progression of a disease. For example, treatment can be the diminishment of one or several symptoms of a disorder or complete eradication of a disorder, such as addiction or withdrawal. Within the meaning of the present disclosure, the term “treat” also denotes a reduction in the risk of worsening a disease. In some embodiments, treatment may be administered after one or more signs or symptoms of the disease have developed or have been observed. In other embodiments, treatment may be administered in the absence of signs or symptoms of the disease. For example, treatment may be administered to a susceptible subject prior to the onset of symptoms (e.g., in light of a history of symptoms and/or in light of exposure to, for example, substances that may lead to substance use disorder or symptoms of withdrawal) Treatment may also be continued after symptoms have resolved, for example, to delay or prevent recurrence. In some embodiments, treatment eliminates symptoms of a disease or disorder. In some embodiments, treatment alleviates, reduces, or lessens the severity of symptoms of a disease or disorder. In some embodiments, treatment prevents the development of symptoms of a disease or disorder, prevents the worsening of symptoms of a disease or disorder, or prevents the development of additional symptoms of a disease or disorder. [0086] The term “prevent,” “preventing” or “prevention” as used herein comprises the prevention of at least one symptom associated with or caused by the state, disease or disorder being prevented. [0087] The term “alkyl” refers to saturated, straight- or branched-chain hydrocarbon moieties containing, in certain embodiments, between one and six, or one and eight carbon atoms, respectively. The number of carbon atoms in an alkyl substituent can be indicated by the prefix “Cx-Cy,” where x is the minimum and y is the maximum number of carbon atoms in the substituent. Likewise, a C_x chain description indicates a group containing x carbon atoms (i.e., not including the number of heteroatoms). Alkyl groups may have from 1 to 20 carbon atoms (“C_1–20 alkyl”). In some embodiments, an alkyl group has 1 to 12 carbon atoms (“C_1–12 alkyl”). In some embodiments, an alkyl group has 1 to 10 carbon atoms (“C_1–10 alkyl”). In some embodiments, an alkyl group has 1 to 9 carbon atoms (“C_1–9 alkyl”). In some embodiments, an alkyl group has 1 to 8 carbon atoms (“C_1–8 alkyl”). In some embodiments, an alkyl group has 1 to 7 carbon atoms (“C_1– ₇ alkyl”). In some embodiments, an alkyl group has 1 to 6 carbon atoms (“C_1–6 alkyl”). In some embodiments, an alkyl group has 1 to 5 carbon atoms (“C1–5 alkyl”). In some embodiments, an alkyl group has 1 to 4 carbon atoms (“C1–4 alkyl”). In some embodiments, an alkyl group has 1 to 3 carbon atoms (“C_1–3 alkyl”). In some embodiments, an alkyl group has 1 to 2 carbon atoms (“C1–2 alkyl”). In some embodiments, an alkyl group has 1 carbon atom (“C1 alkyl”). In some embodiments, an alkyl group has 2 to 6 carbon atoms (“C_2-6 alkyl”). Examples of C₁-C₆-alkyl moieties include, but are not limited to, methyl, ethyl, propyl, isopropyl, n-butyl, tert-butyl, neopentyl, n-hexyl moieties; and examples of C1-C8-alkyl moieties include, but are not limited to, methyl, ethyl, propyl, isopropyl, n-butyl, tert-butyl, neopentyl, n-hexyl, heptyl, and octyl moieties. Unless otherwise specified, each instance of an alkyl group may independently be unsubstituted (an “unsubstituted alkyl”) or substituted (a “substituted alkyl”) with one or more substituents (e.g., halogen, such as F). In certain embodiments, the alkyl group is an unsubstituted C_{1 12} alkyl (such as unsubstituted C_1–6 alkyl, e.g., −CH₃ (Me), unsubstituted ethyl (Et), unsubstituted propyl (Pr, e.g., unsubstituted n-propyl (n-Pr), unsubstituted isopropyl (i-Pr)), unsubstituted butyl (Bu, e.g., unsubstituted n-butyl (n-Bu), unsubstituted tert-butyl (tert-Bu or t-Bu), unsubstituted sec-butyl (sec-Bu or s- Bu), unsubstituted isobutyl (i-Bu)). In certain embodiments, the alkyl group is a substituted C_1–12 alkyl (such as substituted C_1–6 alkyl, e.g., –CH₂F, –CHF₂, –CF₃, – CH₂CH₂F, –CH₂CHF₂, –CH₂CF3, or benzyl (Bn)). [0088] The term “aryl” refers to a mono- or poly-cyclic carbocyclic ring system having one or more aromatic rings, fused or non-fused, including, but not limited to, phenyl (i.e., C6-aryl), naphthyl, tetrahydronaphthyl, indanyl, idenyl, and the like. In some embodiments, aryl groups have 6 carbon atoms (e.g., C₆-aryl or phenyl). In some embodiments, aryl groups have from six to ten carbon atoms (e.g., C₆-C₁₀-aryl). In some embodiments, aryl groups have from six to sixteen carbon atoms. “Aryl” also includes ring systems wherein the aryl ring, as defined above, is fused with one or more carbocyclyl or heterocyclyl groups wherein the radical or point of attachment is on the aryl ring, and in such instances, the number of carbon atoms continue to designate the number of carbon atoms in the aryl ring system. Unless otherwise specified, each instance of an aryl group may independently be unsubstituted (an “unsubstituted aryl”) or substituted (a “substituted aryl”) with one or more substituents. [0089] The term “heteroaryl” refers to a mono- or poly-cyclic (e.g., bi-, or tri-cyclic or more) fused or non-fused moiety or ring system having at least one aromatic ring, where one or more of the ring-forming atoms is a heteroatom such as oxygen, sulfur, or nitrogen. In some embodiments, the heteroaryl group has one to eight carbon atoms, one to six carbon atoms, two to 6 carbon atoms (e.g., C1-C8-heteroaryl, C₁-C₆-heteroaryl, or C₂-C₆-heteroaryl). In further embodiment the heteroaryl group has one to fifteen carbon atoms. In some embodiments, the heteroaryl group contains five to sixteen ring atoms of which one ring atom is selected from oxygen, sulfur, and nitrogen; zero, one, two, or three ring atoms are additional heteroatoms independently selected from oxygen, sulfur, and nitrogen; and the remaining ring atoms are carbon. Heteroaryl includes, but is not limited to, pyridinyl, pyrazinyl, pyrimidinyl, pyrrolyl, pyrazolyl, imidazolyl, thiazolyl, oxazolyl, isooxazolyl, thiazolyl, thiadiazolyl, oxadiazolyl, thiophenyl, furanyl, indolyl, quinolinyl, isoquinolinyl, benzimidazolyl, benzooxazolyl, quinoxalinyl, acridinyl, and the like. In heteroaryl groups that contain one or more nitrogen atoms, the point of attachment can be a carbon or nitrogen atom, as valency permits. Heteroaryl polycyclic ring systems can include one or more heteroatoms in one or both rings. “Heteroaryl” includes ring systems wherein the heteroaryl ring, as defined above, is fused with one or more carbocyclyl or heterocyclyl groups wherein the point of attachment is on the heteroaryl ring, and in such instances, the number of ring members continue to designate the number of ring members in the heteroaryl ring system. “Heteroaryl” also includes ring systems wherein the heteroaryl ring, as defined above, is fused with one or more aryl groups wherein the point of attachment is either on the aryl or heteroaryl ring, and in such instances, the number of ring members designates the number of ring members in the fused polycyclic (aryl/heteroaryl) ring system. Polycyclic heteroaryl groups wherein one ring does not contain a heteroatom (e.g., indolyl, quinolinyl, carbazolyl, and the like) the point of attachment can be on either ring, e.g., either the ring bearing a heteroatom (e.g., 2-indolyl) or the ring that does not contain a heteroatom (e.g., 5-indolyl). In certain embodiments, the heteroaryl is substituted or unsubstituted, 5- or 6-membered, monocyclic heteroaryl, wherein 1, 2, 3, or 4 atoms in the heteroaryl ring system are independently oxygen, nitrogen, or sulfur. In certain embodiments, the heteroaryl is substituted or unsubstituted, 9- or 10-membered, bicyclic heteroaryl, wherein 1, 2, 3, or 4 atoms in the heteroaryl ring system are independently oxygen, nitrogen, or sulfur. [0090] In some embodiments, a heteroaryl group is a 5-10 membered aromatic ring system having ring carbon atoms and 1–4 ring heteroatoms provided in the aromatic ring system, wherein each heteroatom is independently selected from nitrogen, oxygen, and sulfur (“5- 10 membered heteroaryl”). In some embodiments, a heteroaryl group is a 5-8 membered aromatic ring system having ring carbon atoms and 1–4 ring heteroatoms provided in the aromatic ring system, wherein each heteroatom is independently selected from nitrogen, oxygen, and sulfur (“5-8 membered heteroaryl”). In some embodiments, a heteroaryl group is a 5-6 membered aromatic ring system having ring carbon atoms and 1–4 ring heteroatoms provided in the aromatic ring system, wherein each heteroatom is independently selected from nitrogen, oxygen, and sulfur (“5-6 membered heteroaryl”). In some embodiments, the 5-6 membered heteroaryl has 1–3 ring heteroatoms selected from nitrogen, oxygen, and sulfur. In some embodiments, the 5-6 membered heteroaryl has 1–2 ring heteroatoms selected from nitrogen, oxygen, and sulfur. In some embodiments, the 5-6 membered heteroaryl has 1 ring heteroatom selected from nitrogen, oxygen, and sulfur. Unless otherwise specified, each instance of a heteroaryl group is independently unsubstituted (an “unsubstituted heteroaryl”) or substituted (a “substituted heteroaryl”) with one or more substituents. In certain embodiments, the heteroaryl group is an unsubstituted 5-14 membered heteroaryl. In certain embodiments, the heteroaryl group is a substituted 5-14 membered heteroaryl. [0091] Exemplary 5-membered heteroaryl groups containing 1 heteroatom include pyrrolyl, furanyl, and thiophenyl. Exemplary 5-membered heteroaryl groups containing 2 heteroatoms include imidazolyl, pyrazolyl, oxazolyl, isoxazolyl, thiazolyl, and isothiazolyl. Exemplary 5-membered heteroaryl groups containing 3 heteroatoms include triazolyl, oxadiazolyl, and thiadiazolyl. Exemplary 5-membered heteroaryl groups containing 4 heteroatoms include tetrazolyl. Exemplary 6-membered heteroaryl groups containing 1 heteroatom include pyridinyl. Exemplary 6-membered heteroaryl groups containing 2 heteroatoms include pyridazinyl, pyrimidinyl, and pyrazinyl. Exemplary 6- membered heteroaryl groups containing 3 or 4 heteroatoms include triazinyl and tetrazinyl, respectively. Exemplary 7-membered heteroaryl groups containing 1 heteroatom include azepinyl, oxepinyl, and thiepinyl. Exemplary 5,6-bicyclic heteroaryl groups include indolyl, isoindolyl, indazolyl, benzotriazolyl, benzothiophenyl, isobenzothiophenyl, benzofuranyl, benzoisofuranyl, benzimidazolyl, benzoxazolyl, benzisoxazolyl, benzoxadiazolyl, benzthiazolyl, benzisothiazolyl, benzthiadiazolyl, indolizinyl, and purinyl. Exemplary 6,6-bicyclic heteroaryl groups include naphthyridinyl, pteridinyl, quinolinyl, isoquinolinyl, cinnolinyl, quinoxalinyl, phthalazinyl, and quinazolinyl. Exemplary tricyclic heteroaryl groups include phenanthridinyl, dibenzofuranyl, carbazolyl, acridinyl, phenothiazinyl, phenoxazinyl, and phenazinyl. [0092] The term “heterocycloalkyl” refers to a non-aromatic 3-, 4-, 5-, 6- or 7- membered ring or a bi- or tri-cyclic group fused of non-fused system, where (i) each ring contains between one and three heteroatoms independently selected from oxygen, sulfur, and nitrogen and the remaining atoms are carbon (e.g., C2-C6-heterocyclyl, C3-C6- heterocyclyl, or C3-C5-heterocyclyl), (ii) each 5-membered ring has 0 to 1 double bonds and each 6-membered ring has 0 to 2 double bonds, (iii) the nitrogen and sulfur heteroatoms can optionally be oxidized, (iv) the nitrogen heteroatom can optionally be quaternized, and (iv) any of the above rings canbe fused to a benzene ring. The term “heterocycloalkyl” includes, but is not limited to, [1,3]dioxolane, pyrrolidinyl, pyrazolinyl, pyrazolidinyl, imidazolinyl, imidazolidinyl, piperidinyl, piperazinyl, oxazolidinyl, isoxazolidinyl, morpholinyl, thiazolidinyl, isothiazolidinyl, and tetrahydrofuryl. [0093] The term “HDAC” refers to histone deacetylases, which are enzymes that remove the acetyl groups from the lysine residues in core histones, thus leading to the formation of a condensed and transcriptionally silenced chromatin. There are currently 18 known histone deacetylases, which are classified into four groups. Class I HDACs, which include HDAC1, HDAC2, HDAC3, and HDAC8, are related to the yeast RPD3 gene. Class II HDACs, which include HDAC4, HDAC5, HDAC6, HDAC7, HDAC9, and HDAC10, are related to the yeast Hda1 gene. Class III HDACs, which are also known as the sirtuins are related to the Sir2 gene and include SIRT1-7. Class IV HDACs, which contains only HDAC11, has features of both Class I and II HDACs. The term “HDAC” refers to any one or more of the 18 known histone deacetylases, unless otherwise specified. [0094] As used herein, the phrase “substance use disorder” relates to a condition in which there is uncontrolled use of a substance despite harmful consequence. People with a substance use disorder have an intense focus on using a certain substance(s) including alcohol, opioids, psychostimulants, to the point where the person’s ability to function in day to day life becomes impaired. A severe form of substance use disorder is addiction. [0095] The term “withdrawal” refers to physical and mental symptoms that occur after stopping or reducing intake of a substance such as alcohol, opioids and other addictive substances. The characteristics of withdrawal depend on what drug is being discontinued. Symptoms may include anxiety, fatigue, sweating, vomiting, depression, seizures, and hallucinations. [0096] The term “inhibitor” may be used synonymously with the term antagonist. An antagonist is an active agent that binds to the receptor either on the primary site, or on another site, which all together stops the receptor from producing a response, or reduces or slows the response. Inhibitors also include agents that reduce the activity of an enzyme (e.g., HDAC1/2). In some embodiments, inhibitors reduce the activity of an enzyme (e.g., HDAC1/2) to a level that is statistically significantly lower than an initial level, which may, for example, be a baseline level of enzyme activity. In some embodiments, the term refers to a reduction of the level of enzyme activity (e.g., HDAC1/2 activity) to a level that is less than 75%, less than 50%, less than 40%, less than 30%, less than 25%, less than 20%, less than 10%, less than 9%, less than 8%, less than 7%, less than 6%, less than 5%, less than 4%, less than 3%, less than 2%, less than 1%, less than 0.5%, less than 0.1%, less than 0.01%, less than 0.001%, or less than 0.0001% of an initial level, which may for example be a baseline level of enzyme activity. [0097] The term “pharmaceutically acceptable salt” refers to those salts of the compounds formed by the process of the present disclosure which are, within the scope of sound medical judgment, suitable for use in contact with the tissues of humans and lower animals without undue toxicity, irritation, allergic response and the like, and are commensurate with a reasonable benefit/risk ratio. Additionally, “pharmaceutically acceptable salts” refers to derivatives of the disclosed compounds wherein the parent compound is modified by converting an existing acid or base moiety to its salt form. Examples of pharmaceutically acceptable salts include, but are not limited to, mineral or organic acid salts of basic residues such as amines; alkali or organic salts of acidic residues such as carboxylic acids; and the like. The pharmaceutically acceptable salts of the present disclosure include the conventional non-toxic salts of the parent compound formed, for example, from non-toxic inorganic or organic acids. The pharmaceutically acceptable salts of the present disclosure can be synthesized from the parent compound which contains a basic or acidic moiety by conventional chemical methods. Generally, such salts can be prepared by reacting the free acid or base forms of these compounds with a stoichiometric amount of the appropriate base or acid in water or in an organic solvent, or in a mixture of the two; generally, nonaqueous media like ether, ethyl acetate, ethanol, isopropanol, or acetonitrile are preferred. Lists of suitable salts are found in Remington's Pharmaceutical Sciences, 17^th ed., Mack Publishing Company, Easton, Pa., 1985, p.1418 and Journal of Pharmaceutical Science, 66, 2 (1977), each of which is incorporated herein by reference in its entirety. Other pharmaceutically acceptable salts include adipate, alginate, ascorbate, aspartate, benzenesulfonate, benzoate, bisulfate, borate, butyrate, camphorate, camphorsulfonate, citrate, cyclopentanepropionate, digluconate, dodecylsulfate, ethanesulfonate, formate, fumarate, glucoheptonate, glycerophosphate, gluconate, hemisulfate, heptanoate, hexanoate, hydroiodide, 2- hydroxy-ethanesulfonate, lactobionate, lactate, laurate, lauryl sulfate, malate, maleate, malonate, methanesulfonate, 2-naphthalenesulfonate, nicotinate, nitrate, oleate, oxalate, palmitate, pamoate, pectinate, persulfate, 3-phenylpropionate, phosphate, picrate, pivalate, propionate, stearate, succinate, sulfate, tartrate, thiocyanate, p-toluenesulfonate, undecanoate, valerate salts, and the like. Salts derived from appropriate bases include alkali metal, alkaline earth metal, ammonium, and N⁺(C_1-4 alkyl)₄ salts. Representative alkali or alkaline earth metal salts include sodium, lithium, potassium, calcium, magnesium, and the like. Further pharmaceutically acceptable salts include, when appropriate nontoxic ammonium quaternary ammonium, and amine cations formed using counterions such as halide, hydroxide, carboxylate, sulfate, phosphate, nitrate, lower alkyl sulfonate, and aryl sulfonate. [0098] Compounds described herein also include isotopically-labeled compounds wherein one or more atoms is replaced by an atom having the same atomic number, but an atomic mass or mass number different from the atomic mass or mass number usually found in nature. Examples of isotopes suitable for inclusion in the compounds described herein include and are not limited to ²H, ³H, ¹¹C, ¹³C, ¹⁴C, ³⁶Cl, ¹⁸F, ¹²³I, ¹²⁵I, ¹³N, ¹⁵N, ¹⁵O, ¹⁷O, 1⁸O, ³²P, and ³⁵S. In one embodiment, isotopically-labeled compounds are useful in drug and/or substrate tissue distribution studies. In another embodiment, substitution with heavier isotopes such as deuterium affords greater metabolic stability (for example, increased in vivo half-life or reduced dosage requirements). In yet another embodiment, substitution with positron emitting isotopes, such as ¹¹C, ¹⁸F, ¹⁵O and ¹³N, is useful in Positron Emission Topography (PET) studies for examining substrate receptor occupancy. Isotopically-labeled compounds are prepared by any suitable method or by processes using an appropriate isotopically-labeled reagent in place of the non-labeled reagent otherwise employed. [0099] In one embodiment, the compounds described herein are labeled by other means, including, but not limited to, the use of chromophores or fluorescent moieties, bioluminescent labels, or chemiluminescent labels. [0100] The compounds described herein, and related compounds having different substituents can be synthesized using techniques and materials described herein and as described, for example, in Fieser and Fieser's Reagents for Organic Synthesis, Volumes 1-17 (John Wiley and Sons, 1991); Rodd's Chemistry of Carbon Compounds, Volumes 1- 5 and Supplementals (Elsevier Science Publishers, 1989); Organic Reactions, Volumes 1- 40 (John Wiley and Sons, 1991), Larock's Comprehensive Organic Transformations (VCH Publishers Inc., 1989), March, Advanced Organic Chemistry 4^th Ed., (Wiley 1992); Carey and Sundberg, Advanced Organic Chemistry 4th Ed., Vols. A and B (Plenum 2000,2001), and Green and Wuts, Protective Groups in Organic Synthesis 3rd Ed., (Wiley 1999) (all of which are incorporated by reference for such disclosure). General methods for the preparation of compound as described herein are modified by the use of appropriate reagents and conditions, for the introduction of the various moieties found in the formula as provided herein. [0101] Compounds described herein can be synthesized using any suitable procedures starting from compounds that are available from commercial sources, or can be prepared using procedures described in PCT application PCT/US2017/016067 (WO 2017/136451) the content of which is hereby incorporated by reference in its entirety. Methods for Treating [0102] Provided herein are methods for treating or preventing disorders in a subject, such as a human or other animal, by administering to the subject a therapeutically effective amount of a compound provided herein, in such amounts and for such time as is necessary to achieve the desired result. [0103] In an aspect, provided herein is a method of treating a substance use disorder in a subject in need thereof, comprising administering to the subject a therapeutically effective amount of a histone deacetylase 1/2 (HDAC1/2) inhibitor. [0104] In an embodiment, the HDAC1/2 inhibitor is a compound of Formula I:

I, or a pharmaceutically acceptable salt thereof, wherein R¹ is aryl or heteroaryl; R² is H, C₁-C₆-alkyl, or C₁-C₆-alkyl-N(R^a)2; R³ is H, C₁-C₆-alkyl, C₁-C₆-alkyl-N(R^a)₂, or C(O)R^b; or R² and R³, together with the N atom to which they are attached, optionally form a 5 or 6 membered heterocycloalkyl ring, wherein the heterocycloalkyl ring optionally contains a -N(R^c)- moiety and wherein the heterocycloalkyl ring optionally contains a -C(O)- moiety; each R^a is independently H or C₁-C₆-alkyl; R^b is C₁-C₆-alkyl, C₁-C₆-alkyl-N(R^d)2, or a 5 or 6 membered heterocycloalkyl, wherein the heterocycloalkyl is optionally substituted by C₁-C₆-alkyl; R^c is H or C₁-C₆-alkyl; and each R^d is independently H or C₁-C₆-alkyl. [0105] In another embodiment, R¹ is phenyl, thiophenyl, or pyridinyl. In yet another embodiment, R¹ is phenyl. [0106] In still another embodiment, R² is H or C₁-C₆-alkyl; R³ is C₁-C₆-alkyl-N(R^a)₂ or C(O)R^b; or R² and R³, together with the N atom to which they are attached, optionally form a 5 or 6 membered heterocycloalkyl ring, wherein the heterocycloalkyl ring optionally contains a -C(O)- moiety and wherein the heterocycloalkyl ring optionally contains a -N(R^c)- moiety. [0107] In an embodiment, R² and R³, together with the N atom to which they are attached, form piperadine, piperazine, or piperidinone. [0108] In another embodiment, the HDAC1/2 inhibitor is a compound of Formula II:

II, or a pharmaceutically acceptable salt thereof, wherein R¹ is aryl or heteroaryl; andR^c is H or C₁-C₆-alkyl. In yet another embodiment, R^c is H. In still another embodiment, the HDAC1/2 inhibitor is Compound A

Compound A; or a pharmaceutically acceptable salt thereof. [0109] In another aspect, provided herein is a method of treating a substance use disorder in a subject in need thereof, comprising administering to the subject a therapeutically effective amount of Compound A:

Compound A; or a pharmaceutically acceptable salt thereof. [0110] In another aspect, provided herein is a method of treating addiction withdrawal in a subject in need thereof, comprising administering to the subject a therapeutically effective amount of Compound A:

Compound A; or a pharmaceutically acceptable salt thereof. [0111] In yet another aspect, provided herein is a method of treating a substance use disorder in a subject in need thereof, comprising administering to the subject a therapeutically effective amount of a histone deacetylase 1/2 (HDAC1/2) inhibitor, wherein the subject experiences pain symptoms. In still another aspect, provided herein is a method of treating addiction withdrawal in a subject in need thereof, comprising administering to the subject a therapeutically effective amount of a histone deacetylase 1/2 (HDAC1/2) inhibitor, wherein the subject experiences pain symptoms. [0112] In some embodiments the HDAC1/2 inhibitor is selected from the group consisting of Vorinostat, Romidepsin, Panobinostat, and Belinostat. [0113] In another aspect, provided herein is a method of treating addiction withdrawal in a subject in need thereof, comprising administering to the subject a therapeutically effective amount of any one of the major classes of HDAC inhibitors, such as those described in Kim et al., “Histone deacetylase inhibitors: molecular mechanisms of action and clinical trials as anti-cancer drugs” Am. J. Transl. Res 2011; 3(2):166-179, which is herein incorporated by reference in its entirety [0114] In another aspect, provided herein is a method of treating addiction withdrawal in a subject in need thereof, comprising administering to the subject a therapeutically effective amount of a hydroxamic acid-based pan-HDAC inhibitors. A non-limiting example of a hydroxamic acid-based pan-HDAC inhibitor is shown as Compound B (e.g., SAHA, Vorinostat, Zolinza). [0115]

Compound B [0116] A second non-limiting example of a hydroxamic acid-based pan-HDAC inhibitor is shown as Compound C (e.g., TSA). [0117]

Compound C [0118] A third non-limiting example of a hydroxamic acid-based pan-HDAC inhibitor is shown as Compound D (e.g., PXD-101).

Compound D [0119] In another aspect, provided herein is a method of treating addiction withdrawal in a subject in need thereof, comprising administering to the subject a therapeutically effective amount of a synthetic benzamide derived-HDAC inhibitor. A non-limiting example of a synthetic benzamide derived HDAC inhibitor are shown as Compound E (e.g., MS-275) and Compound F (e.g., MGCD0103)

[0120] In another aspect, provided herein is a method of treating addiction withdrawal in a subject in need thereof, comprising administering to the subject a therapeutically effective amount of a prodrug natural cyclic peptide HDAC inhibitor. A non-limiting example of a prodrug cyclic peptide HDAC inhibitor is shown as Compound G (e.g., Desipeptide/FK228/romidepsin/ISTODAX).

[0121] In another aspect, provided herein is a method of treating addiction withdrawal in a subject in need thereof, comprising administering to the subject a therapeutically effective amount of an aliphatic acid-derived HDAC inhibitor. Non-limiting examples of a aliphatic acid-derived HDAC inhibitors are shown as Compound H (e.g., Valproic acid) and Compound I (e.g., sodium phenylbutyrate).

[0122] In an embodiment, the subject is addicted to one or more substances selected from the group consisting of alcohol, an opioid, an opiate, and cocaine. [0123] In another embodiment, the subject is addicted to alcohol. In yet another embodiment, the subject is addicted to an opioid. In still another embodiment, the subject is addicted to an opiate. In an embodiment, the subject is addicted to cocaine. [0124] In another embodiment, the opioid is selected from the group consisting of oxycodone, hydrocodone, morphine, oxymorphone, fentanyl, codeine, and tramadol. In yet another embodiment, the opioid is oxycodone, morphine, or fentanyl. In still another embodiment, the opioid is oxycodone. [0125] In an embodiment, the method comprises reducing one or more symptoms of a substance use disorder or withdrawal. [0126] In another embodiment, the substance use disorder or withdrawal symptom is selected from the group consisting of mechanical hypersensitivity, hyperalgesia, peripheral nerve damage, anxiety, depression, avolition, and photophobia. [0127] In yet another embodiment, wherein the mechanical hypersensitivity is mechanical allodynia. In still another embodiment, the substance use disorder or withdrawal symptom is hyperalgesia. In an embodiment, the hyperalgesia is thermal hyperalgesia. [0128] In another embodiment of the methods, the subject in need thereof experiences pain symptoms. [0129] As described elsewhere herein, methods of diagnosing a subject with a substance use disorder are known in the art and may be found, for example, the Diagnostic and Statistical Manual of Mental Disorders, 5^th edition (DSM-5) published by the American Psychiatric Association on May 18, 2013 and in Hasin et al., “DSM-5 Criteria for Substance Use Disorders: Recommendations and Rationale” Am. J. Psychiatry. 2013 Aug 1; 170(8): 834-851, both of which, are hereby incorporated by reference in their entirety. Without wishing to be bound by theory, according to DSM-5, a substance use disorder involved patterns of symptoms caused by using a substance that an individual continues taking despite its negative effects. The DSM-5 points out 11 criteria that can arise from substance misuse. [0130] Those in the art familiar with the DSM-5 criteria, will understand that the above recited criteria allow a clinician (e.g., medical doctor, nurse practitioner, physician’s assistant, etc.) to determine the severity of a substance use disorder depending on the number of criteria met. For example, a subject exhibiting any one of the eleven symptoms indicates the subject is at risk of developing a substance use disorder. A subject exhibiting two or three criteria may be diagnosed as having a mild substance use disorder. A subject exhibiting four or five criteria may be diagnosed as having a moderate substance use disorder. A subject exhibiting six or more criteria may be diagnosed as having a severe substance use disorder and an addition to a particular substance [0131] In general, compounds of the present disclosure will be administered in therapeutically effective amounts via any of the usual and acceptable modes known in the art, either singly or in combination with one or more therapeutic agents. A therapeutically effective amount can vary widely depending on the severity of the disease, the age and relative health of the subject, the potency of the compound used and other factors. [0132] In certain embodiments, a therapeutic amount or dose of the compounds of the present disclosure can range from about 0.1 mg/kg to about 500 mg/kg (about 0.18 mg/m² to about 900 mg/m²), alternatively from about 1 to about 50 mg/kg (about 1.8 to about 90 mg/m²). In general, treatment regimens according to the present disclosure comprise administration to a subject in need of such treatment from about 10 mg to about 1000 mg of the compound(s) of this disclosure per day in single or multiple doses. Therapeutic amounts or doses will also vary depending on route of administration, as well as the possibility of co-usage with other agents. [0133] Upon improvement of a subject’s condition, a maintenance dose of a compound, composition or combination of this disclosure can be administered, if necessary. Subsequently, the dosage or frequency of administration, or both, can be reduced, as a function of the symptoms, to a level at which the improved condition is retained when the symptoms have been alleviated to the desired level, treatment should cease. The subject can, however, require intermittent treatment on a long-term basis upon any recurrence of disease symptoms. [0134] It will be understood, however, that the total daily usage of the compounds and compositions of the present disclosure will be decided by the attending physician within the scope of sound medical judgment. The specific inhibitory dose for any particular subject (or patient) will depend upon a variety of factors including the disorder being treated and the severity of the disorder; the activity of the specific compound employed; the specific composition employed; the age, body weight, general health, sex and diet of the subject; the time of administration, route of administration, and rate of excretion of the specific compound employed; the duration of the treatment; drugs used in combination or coincidental with the specific compound employed; and like factors well known in the medical arts. Pharmaceutical Compositions [0135] The compounds provided herein can be administered as pharmaceutical compositions by any conventional route, in particular enterally, for example, orally, e.g., in the form of tablets or capsules, or parenterally, e.g., in the form of injectable solutions or suspensions, topically, e.g., in the form of lotions, gels, ointments or creams, or in a nasal or suppository form. [0136] Pharmaceutical compositions comprising a compound provided herein in free form or in a pharmaceutically acceptable salt form in association with at least one pharmaceutically acceptable carrier or diluent can be manufactured in a conventional manner by mixing, granulating or coating methods. For example, oral compositions can be tablets or gelatin capsules comprising the active ingredient together with a) diluents, e.g., lactose, dextrose, sucrose, mannitol, sorbitol, cellulose and/or glycine; b) lubricants, e.g., silica, talcum, stearic acid, its magnesium or calcium salt and/or polyethyleneglycol; for tablets also c) binders, e.g., magnesium aluminum silicate, starch paste, gelatin, tragacanth, methylcellulose, sodium carboxymethylcellulose and or polyvinylpyrrolidone; if desired d) disintegrants, e.g., starches, agar, alginic acid or its sodium salt, or effervescent mixtures; and/or e) absorbents, colorants, flavors and sweeteners. Injectable compositions can be aqueous isotonic solutions or suspensions, and suppositories can be prepared from fatty emulsions or suspensions. The compositions can be sterilized and/or contain adjuvants, such as preserving, stabilizing, wetting or emulsifying agents, solution promoters, salts for regulating the osmotic pressure and/or buffers. In addition, they can also contain other therapeutically valuable substances. Suitable formulations for transdermal applications include an effective amount of a compound of the present disclosure with a carrier. A carrier can include absorbable pharmacologically acceptable solvents to assist passage through the skin of the host. For example, transdermal devices are in the form of a bandage comprising a backing member, a reservoir containing the compound optionally with carriers, optionally a rate controlling barrier to deliver the compound to the skin of the host at a controlled and predetermined rate over a prolonged period of time, and means to secure the device to the skin. Matrix transdermal formulations can also be used. Suitable formulations for topical application, e.g., to the skin and eyes, are preferably aqueous solutions, ointments, creams or gels well-known in the art. Such can contain solubilizers, stabilizers, tonicity enhancing agents, buffers and preservatives. [0137] The solid dosage forms of tablets, dragees, capsules, pills, and granules can be prepared with coatings and shells such as enteric coatings, release controlling coatings and other coatings well known in the pharmaceutical formulating art. In such solid dosage forms the active compound can be admixed with at least one inert diluent such as sucrose, lactose or starch. Such dosage forms can also comprise, as is normal practice, additional substances other than inert diluents, e.g., tableting lubricants and other tableting aids such a magnesium stearate and microcrystalline cellulose. In the case of capsules, tablets and pills, the dosage forms can also comprise buffering agents. [0138] In certain embodiments, the compounds described herein are provided in an effective amount in the pharmaceutical composition. In certain embodiments, the effective amount is a therapeutically effective amount. In certain embodiments, the effective amount is a prophylactically effective amount. In certain embodiments, the effective amount is an amount effective for treating a substance use disorder and/or symptoms of withdrawal. In certain embodiments, the effective amount is an amount effective for preventing a substance use disorder and/or symptoms of withdrawal. In certain embodiments, the effective amount is an amount effective for reducing the risk of developing a substance use disorder and/or symptoms of withdrawal. In certain embodiments, the effective amount is an amount effective for inhibiting the activity of HDAC1/2. [0139] In certain embodiments, the subject is an animal. The animal may be of either sex and may be at any stage of development. In certain embodiments, the subject described herein is a human. In certain embodiments, the subject is a non-human animal. In certain embodiments, the subject is a mammal. In certain embodiments, the subject is a non- human mammal. In certain embodiments, the subject is a domesticated animal, such as a dog, cat, cow, pig, horse, sheep, or goat. In certain embodiments, the subject is a companion animal, such as a dog or cat. In certain embodiments, the subject is a livestock animal, such as a cow, pig, horse, sheep, or goat. In certain embodiments, the subject is a zoo animal In another embodiment the subject is a research animal, such as a rodent (e.g., mouse, rat), dog, pig, or non-human primate. In certain embodiments, the animal is a genetically engineered animal. In certain embodiments, the animal is a transgenic animal (e.g., transgenic mice and transgenic pigs). In certain embodiments, the subject is a fish or reptile. [0140] In certain embodiments, the effective amount is an amount effective for inhibiting the activity of HDAC1/2 by at least about 10%, at least about 20%, at least about 30%, at least about 40%, at least about 50%, at least about 60%, at least about 70%, at least about 80%, at least about 90%, at least about 95%, or at least about 98%. In certain embodiments, the effective amount is an amount effective for inhibiting the activity of HDAC1/2 by not more than 10%, not more than 20%, not more than 30%, not more than 40%, not more than 50%, not more than 60%, not more than 70%, not more than 80%, not more than 90%, not more than 95%, or not more than 98%. In certain embodiments, the effective amount is an amount effective for inhibiting the activity of HDAC1/2 by a range between a percentage described in this paragraph and another percentage described in this paragraph, inclusive. [0141] Pharmaceutical compositions described herein can be prepared by any method known in the art of pharmaceutics. In general, such preparatory methods include bringing the compound described herein (i.e., the “active ingredient”) into association with a carrier or excipient, and/or one or more other accessory ingredients, and then, if necessary and/or desirable, shaping, and/or packaging the product into a desired single- or multi-dose unit. [0142] Pharmaceutical compositions can be prepared, packaged, and/or sold in bulk, as a single unit dose, and/or as a plurality of single unit doses. A “unit dose” is a discrete amount of the pharmaceutical composition comprising a predetermined amount of the active ingredient. The amount of the active ingredient is generally equal to the dosage of the active ingredient which would be administered to a subject and/or a convenient fraction of such a dosage, such as one-half or one-third of such a dosage. [0143] Relative amounts of the active ingredient, the pharmaceutically acceptable excipient, and/or any additional ingredients in a pharmaceutical composition described herein will vary, depending upon the identity, size, and/or condition of the subject treated and further depending upon the route by which the composition is to be administered. The composition may comprise between 0.1% and 100% (w/w) active ingredient. [0144] Pharmaceutically acceptable excipients used in the manufacture of provided pharmaceutical compositions include inert diluents, dispersing and/or granulating agents, surface active agents and/or emulsifiers disintegrating agents, binding agents, preservatives, buffering agents, lubricating agents, and/or oils. Excipients such as cocoa butter and suppository waxes, coloring agents, coating agents, sweetening, flavoring, and perfuming agents may also be present in the composition. [0145] Exemplary diluents include calcium carbonate, sodium carbonate, calcium phosphate, dicalcium phosphate, calcium sulfate, calcium hydrogen phosphate, sodium phosphate lactose, sucrose, cellulose, microcrystalline cellulose, kaolin, mannitol, sorbitol, inositol, sodium chloride, dry starch, cornstarch, powdered sugar, and mixtures thereof. [0146] Exemplary granulating and/or dispersing agents include potato starch, corn starch, tapioca starch, sodium starch glycolate, clays, alginic acid, guar gum, citrus pulp, agar, bentonite, cellulose, and wood products, natural sponge, cation-exchange resins, calcium carbonate, silicates, sodium carbonate, cross-linked poly(vinyl-pyrrolidone) (crospovidone), sodium carboxymethyl starch (sodium starch glycolate), carboxymethyl cellulose, cross-linked sodium carboxymethyl cellulose (croscarmellose), methylcellulose, pregelatinized starch (starch 1500), microcrystalline starch, water insoluble starch, calcium carboxymethyl cellulose, magnesium aluminum silicate (Veegum), sodium lauryl sulfate, quaternary ammonium compounds, and mixtures thereof. [0147] Exemplary surface active agents and/or emulsifiers include natural emulsifiers (e.g., acacia, agar, alginic acid, sodium alginate, tragacanth, chondrux, cholesterol, xanthan, pectin, gelatin, egg yolk, casein, wool fat, cholesterol, wax, and lecithin), colloidal clays (e.g., bentonite (aluminum silicate) and Veegum (magnesium aluminum silicate)), long chain amino acid derivatives, high molecular weight alcohols (e.g., stearyl alcohol, cetyl alcohol, oleyl alcohol, triacetin monostearate, ethylene glycol distearate, glyceryl monostearate, and propylene glycol monostearate, polyvinyl alcohol), carbomers (e.g., carboxy polymethylene, polyacrylic acid, acrylic acid polymer, and carboxyvinyl polymer), carrageenan, cellulosic derivatives (e.g., carboxymethylcellulose sodium, powdered cellulose, hydroxymethyl cellulose, hydroxypropyl cellulose, hydroxypropyl methylcellulose, methylcellulose), sorbitan fatty acid esters (e.g., polyoxyethylene sorbitan monolaurate (Tween^® 20), polyoxyethylene sorbitan (Tween^® 60), polyoxyethylene sorbitan monooleate (Tween^® 80), sorbitan monopalmitate (Span^® 40), sorbitan monostearate (Span^® 60), sorbitan tristearate (Span^® 65), glyceryl monooleate, sorbitan monooleate (Span^® 80), polyoxyethylene esters (e.g., polyoxyethylene monostearate (Myrj^® 45), polyoxyethylene hydrogenated castor oil, polyethoxylated castor oil polyoxymethylene stearate and Solutol^®), sucrose fatty acid esters, polyethylene glycol fatty acid esters (e.g., Cremophor^®), polyoxyethylene ethers, (e.g., polyoxyethylene lauryl ether (Brij^® 30)), poly(vinyl-pyrrolidone), diethylene glycol monolaurate, triethanolamine oleate, sodium oleate, potassium oleate, ethyl oleate, oleic acid, ethyl laurate, sodium lauryl sulfate, Pluronic^® F-68, poloxamer P-188, cetrimonium bromide, cetylpyridinium chloride, benzalkonium chloride, docusate sodium, and/or mixtures thereof. [0148] Exemplary binding agents include starch (e.g., cornstarch and starch paste), gelatin, sugars (e.g., sucrose, glucose, dextrose, dextrin, molasses, lactose, lactitol, mannitol, etc.), natural and synthetic gums (e.g., acacia, sodium alginate, extract of Irish moss, panwar gum, ghatti gum, mucilage of isapol husks, carboxymethylcellulose, methylcellulose, ethylcellulose, hydroxyethylcellulose, hydroxypropyl cellulose, hydroxypropyl methylcellulose, microcrystalline cellulose, cellulose acetate, poly(vinyl-pyrrolidone), magnesium aluminum silicate (Veegum^®), and larch arabogalactan), alginates, polyethylene oxide, polyethylene glycol, inorganic calcium salts, silicic acid, polymethacrylates, waxes, water, alcohol, and/or mixtures thereof. [0149] Exemplary preservatives include antioxidants, chelating agents, antimicrobial preservatives, antifungal preservatives, antiprotozoan preservatives, alcohol preservatives, acidic preservatives, and other preservatives. In certain embodiments, the preservative is an antioxidant. In other embodiments, the preservative is a chelating agent. [0150] Exemplary antioxidants include alpha tocopherol, ascorbic acid, ascorbyl palmitate, butylated hydroxyanisole, butylated hydroxytoluene, monothioglycerol, potassium metabisulfite, propionic acid, propyl gallate, sodium ascorbate, sodium bisulfite, sodium metabisulfite, and sodium sulfite. [0151] Exemplary chelating agents include ethylenediaminetetraacetic acid (EDTA) and salts and hydrates thereof (e.g., sodium edetate, disodium edetate, trisodium edetate, calcium disodium edetate, dipotassium edetate, and the like), citric acid and salts and hydrates thereof (e.g., citric acid monohydrate), fumaric acid and salts and hydrates thereof, malic acid and salts and hydrates thereof, phosphoric acid and salts and hydrates thereof, and tartaric acid and salts and hydrates thereof. Exemplary antimicrobial preservatives include benzalkonium chloride, benzethonium chloride, benzyl alcohol, bronopol, cetrimide, cetylpyridinium chloride, chlorhexidine, chlorobutanol, chlorocresol, chloroxylenol, cresol, ethyl alcohol, glycerin, hexetidine, imidurea, phenol, phenoxyethanol, phenylethyl alcohol, phenylmercuric nitrate, propylene glycol, and thimerosal. [0152] Exemplary antifungal preservatives include butyl paraben, methyl paraben, ethyl paraben, propyl paraben, benzoic acid, hydroxybenzoic acid, potassium benzoate, potassium sorbate, sodium benzoate, sodium propionate, and sorbic acid. [0153] Exemplary alcohol preservatives include ethanol, polyethylene glycol, phenol, phenolic compounds, bisphenol, chlorobutanol, hydroxybenzoate, and phenylethyl alcohol. [0154] Exemplary acidic preservatives include vitamin A, vitamin C, vitamin E, beta- carotene, citric acid, acetic acid, dehydroacetic acid, ascorbic acid, sorbic acid, and phytic acid. [0155] Other preservatives include tocopherol, tocopherol acetate, deteroxime mesylate, cetrimide, butylated hydroxyanisol (BHA), butylated hydroxytoluened (BHT), ethylenediamine, sodium lauryl sulfate (SLS), sodium lauryl ether sulfate (SLES), sodium bisulfite, sodium metabisulfite, potassium sulfite, potassium metabisulfite, Glydant^® Plus, Phenonip^®, methylparaben, Germall^® 115, Germaben^® II, Neolone^®, Kathon^®, and Euxyl^®. [0156] Exemplary buffering agents include citrate buffer solutions, acetate buffer solutions, phosphate buffer solutions, ammonium chloride, calcium carbonate, calcium chloride, calcium citrate, calcium glubionate, calcium gluceptate, calcium gluconate, D-gluconic acid, calcium glycerophosphate, calcium lactate, propanoic acid, calcium levulinate, pentanoic acid, dibasic calcium phosphate, phosphoric acid, tribasic calcium phosphate, calcium hydroxide phosphate, potassium acetate, potassium chloride, potassium gluconate, potassium mixtures, dibasic potassium phosphate, monobasic potassium phosphate, potassium phosphate mixtures, sodium acetate, sodium bicarbonate, sodium chloride, sodium citrate, sodium lactate, dibasic sodium phosphate, monobasic sodium phosphate, sodium phosphate mixtures, tromethamine, magnesium hydroxide, aluminum hydroxide, alginic acid, pyrogen-free water, isotonic saline, Ringer’s solution, ethyl alcohol, and mixtures thereof. [0157] Exemplary lubricating agents include magnesium stearate, calcium stearate, stearic acid, silica, talc, malt, glyceryl behanate, hydrogenated vegetable oils, polyethylene glycol, sodium benzoate, sodium acetate, sodium chloride, leucine, magnesium lauryl sulfate, sodium lauryl sulfate, and mixtures thereof. [0158] Exemplary natural oils include almond, apricot kernel, avocado, babassu, bergamot, black current seed, borage, cade, camomile, canola, caraway, carnauba, castor, cinnamon, cocoa butter coconut cod liver coffee corn cotton seed, emu, eucalyptus, evening primrose, fish, flaxseed, geraniol, gourd, grape seed, hazel nut, hyssop, isopropyl myristate, jojoba, kukui nut, lavandin, lavender, lemon, litsea cubeba, macademia nut, mallow, mango seed, meadowfoam seed, mink, nutmeg, olive, orange, orange roughy, palm, palm kernel, peach kernel, peanut, poppy seed, pumpkin seed, rapeseed, rice bran, rosemary, safflower, sandalwood, sasquana, savoury, sea buckthorn, sesame, shea butter, silicone, soybean, sunflower, tea tree, thistle, tsubaki, vetiver, walnut, and wheat germ oils. Exemplary synthetic oils include, but are not limited to, butyl stearate, caprylic triglyceride, capric triglyceride, cyclomethicone, diethyl sebacate, dimethicone 360, isopropyl myristate, mineral oil, octyldodecanol, oleyl alcohol, silicone oil, and mixtures thereof. [0159] A compound or composition, as described herein, can be administered in combination with one or more additional pharmaceutical agents (e.g., therapeutically and/or prophylactically active agents). The compounds or compositions can be administered in combination with additional pharmaceutical agents that improve their activity (e.g., activity (e.g., potency and/or efficacy) in treating a disease in a subject in need thereof, in preventing a disease in a subject in need thereof, in reducing the risk to develop a disease in a subject in need thereof, and/or in inhibiting the activity of a protein kinase in a subject or cell), improve bioavailability, improve safety, reduce drug resistance, reduce and/or modify metabolism, inhibit excretion, and/or modify distribution in a subject or cell. It will also be appreciated that the therapy employed may achieve a desired effect for the same disorder, and/or it may achieve different effects. In certain embodiments, a pharmaceutical composition described herein including a compound described herein and an additional pharmaceutical agent shows a synergistic effect that is absent in a pharmaceutical composition including one of the compound and the additional pharmaceutical agent, but not both. In some embodiments, the additional pharmaceutical agent achieves a desired effect for the same disorder. In some embodiments, the additional pharmaceutical agent achieves different effects. [0160] The compound or composition can be administered concurrently with, prior to, or subsequent to one or more additional pharmaceutical agents, which may be useful as, e.g., combination therapies. Pharmaceutical agents include therapeutically active agents. Pharmaceutical agents also include prophylactically active agents. Pharmaceutical agents include small organic molecules such as drug compounds (e.g., compounds approved for human or veterinary use by the U.S. Food and Drug Administration as provided in the Code of Federal Regulations (CFR)) peptides proteins, carbohydrates, monosaccharides, oligosaccharides, polysaccharides, nucleoproteins, mucoproteins, lipoproteins, synthetic polypeptides or proteins, small molecules linked to proteins, glycoproteins, steroids, nucleic acids, DNAs, RNAs, nucleotides, nucleosides, oligonucleotides, antisense oligonucleotides, lipids, hormones, vitamins, and cells. In certain embodiments, the additional pharmaceutical agent is a pharmaceutical agent useful for treating and/or preventing a disease (e.g., a substance use disorder and/or symptoms of withdrawal). Each additional pharmaceutical agent may be administered at a dose and/or on a time schedule determined for that pharmaceutical agent. The additional pharmaceutical agents may also be administered together with each other and/or with the compound or composition described herein in a single dose or composition or administered separately in different doses or compositions. The particular combination to employ in a regimen will take into account compatibility of the compound described herein with the additional pharmaceutical agent(s) and/or the desired therapeutic and/or prophylactic effect to be achieved. In general, it is expected that the additional pharmaceutical agent(s) in combination be utilized at levels that do not exceed the levels at which they are utilized individually. In some embodiments, the levels utilized in combination will be lower than those utilized individually. [0161] Also encompassed by the disclosure are kits (e.g., pharmaceutical packs). The kits provided may comprise a pharmaceutical composition or compound described herein and a container (e.g., a vial, ampule, bottle, syringe, and/or dispenser package, or other suitable container). In some embodiments, provided kits may optionally further include a second container comprising a pharmaceutical excipient for dilution or suspension of a pharmaceutical composition or compound described herein. In some embodiments, the pharmaceutical composition or compound described herein provided in the first container and the second container are combined to form one unit dosage form. [0162] Thus, in one aspect, provided are kits including a first container comprising a compound or pharmaceutical composition described herein. In certain embodiments, the kits are useful for treating a disease (e.g., a substance use disorder and/or symptoms of withdrawal) in a subject in need thereof. In certain embodiments, the kits are useful for preventing a disease (e.g., a substance use disorder and/or symptoms of withdrawal) in a subject in need thereof. In certain embodiments, the kits are useful for reducing the risk of developing a disease (e.g., a substance use disorder and/or symptoms of withdrawal) in a subject in need thereof. In certain embodiments, the kits are useful for inhibiting the activity of HDAC1/2 in a subject or cell [0163] In certain embodiments, a kit described herein further includes instructions for using the kit. A kit described herein may also include information as required by a regulatory agency such as the U.S. Food and Drug Administration (FDA). In certain embodiments, the information included in the kits is prescribing information. In certain embodiments, the kits and instructions provide for treating a disease (e.g., a substance use disorder and/or symptoms of withdrawal) in a subject in need thereof. In certain embodiments, the kits and instructions provide for preventing a disease (e.g., a substance use disorder and/or symptoms of withdrawal) in a subject in need thereof. In certain embodiments, the kits and instructions provide for reducing the risk of developing a disease (e.g., a substance use disorder and/or symptoms of withdrawal) in a subject in need thereof. In certain embodiments, the kits and instructions provide for inhibiting the activity of HDAC1/2 in a subject or a cell. A kit described herein may include one or more additional pharmaceutical agents described herein as a separate composition. [0164] Methods delineated herein include those wherein the subject is identified as in need of a particular stated treatment. Identifying a subject in need of such treatment can be in the judgment of a subject or a health care professional and can be subjective (e.g. opinion) or objective (e.g. measurable by a test or diagnostic method). [0165] In certain embodiments, the disclosure provides a method for treating of any of the disorders described herein, wherein the subject is a human. [0166] The disclosed subject matter is not to be limited in scope by the specific embodiments and examples described herein. Indeed, various modifications of the disclosure in addition to those described will become apparent to those skilled in the art from the foregoing description and accompanying figures. Such modifications are intended to fall within the scope of the appended claims. [0167] All references (e.g., publications or patents or patent applications) cited herein are incorporated herein by reference in their entirety and for all purposes to the same extent as if each individual reference (e.g., publication or patent or patent application) was specifically and individually indicated to be incorporated by reference in its entirety for all purposes. Other embodiments are within the following claims. [0168] The following examples further illustrate aspects of the present disclosure. However, they are in no way a limitation of the teachings or disclosure of the present disclosure as set forth herein. EXAMPLES Transcriptomic signatures of oxycodone withdrawal in brain reward circuitry in the presence or absence of chronic pain: HDAC1/2 inhibition attenuating opioid withdrawal under chronic pain states [0170] The development of physical dependence and addiction disorders due to misuse of opioid analgesics is a major concern with pain therapeutics. A mouse model of oxycodone exposure was used to gain insight into genes and molecular pathways in reward-related brain regions that are affected by prolonged exposure to oxycodone and subsequent withdrawal in the presence or absence of chronic neuropathic pain. RNA- Sequencing (RNA-Seq) and bioinformatic analyses revealed that oxycodone withdrawal alone triggers robust gene expression adaptations in the nucleus accumbens (NAc), medial prefrontal cortex (mPFC), and ventral tegmental area (VTA), with numerous genes and pathways selectively affected by oxycodone withdrawal under peripheral nerve injury states. A pathway analysis predicted that histone deacetylase 1 (HDAC1), an epigenetic modifier with a prominent role in striatal plasticity, is a top upstream regulator in opioid withdrawal in both the NAc and mPFC. Indeed, treatment with the novel HDAC1/2 inhibitor RBC1HI (Regenacy Brain Class 1 HDAC Inhibitor) attenuated behavioral manifestations of oxycodone withdrawal, with the drug being more efficacious under states of neuropathic pain. Since RBC1HI displays antiallodynic actions in models of neuropathic pain, inhibition of HDAC1/2 may provide an avenue for chronic pain patients dependent on opioids to transition to non-opioid analgesics. Overall, this study highlights transcriptomic events in components of the reward circuitry associated with oxycodone withdrawal under pain-free and prolonged neuropathic pain states, thereby providing information on possible new targets for the treatment of physical dependence to opioids and transitioning individuals to non-opioid medications for chronic pain management. [0171] Synthetic opioids are used successfully to alleviate acute and postoperative pain¹. By contrast, the prescription of opioid analgesics for chronic neuropathic pain conditions has been particularly problematic, as they show limited efficacy and only alleviate a subset of symptoms2, 3, 4, 5, 6. Moreover, prolonged use of opioids leads to severe side effects, including hyperalgesia, physical dependence, and often transition to addiction^{1, 7}. The dopaminergic mesocorticolimbic brain circuitry is highly dysregulated under states of physical dependence and addiction^{8, 9}. The brain’s reward circuitry also plays a prominent role in the perception and processing of chronic pain symptoms in humans as well as in preclinical models^{2, 10, 11, 12, 13}. While numerous studies have investigated the mechanisms underlying opioid actions in components of the reward circuitry^{1, 14, 15}, much less is known about the lasting actions of opioids under chronic neuropathic pain states. Several human studies have documented changes in the activity of the nucleus accumbens (NAc) and other reward circuitry components that correlate with chronic pain states^{11, 16.} The prevalence of addiction and physical dependence is especially high among chronic pain patients. Clinical studies document exacerbation of pain states among opioid-dependent chronic pain patients and report pain reduction upon detoxification from opioids^{17, 18, 19}. Current treatments for opioid use disorders, such as buprenorphine/naloxone, may promote hyperalgesia in chronic pain patients²⁰. Furthermore, since a large number of pain patients obtain opioids illicitly, there is risk for acute withdrawal if the buprenorphine/naloxone regimen is not carefully tapered²⁰. Methadone substitution therapy requires frequent clinic visits, which is particularly difficult for chronic pain patients^{19, 20}. Identification of non-opioid medications that alleviate pain while attenuating withdrawal will represent a major advance in the field. [0172] The inventors previously demonstrated robust gene expression adaptations in the murine NAc and mPFC in response to peripheral nerve injury²¹ and antidepressant drug treatment under nerve injury states²². Furthermore, the inventors have shown that interventions in gene expression or in the activity of brain reward sub-regions robustly affects behavioral manifestations of peripheral nerve injury as well as the efficacy of therapeutic compounds^{13, 22, 23, 24, 25}. However, the field currently lacks an understanding of how coincident chronic pain impacts transcriptional responses to chronic opioid administration. [0173] In this example, the inventors established a new mouse paradigm that allowed better understanding of the impact of chronic opioid exposure and physical dependence under chronic pain states on genome-wide events in components of the brain reward circuitry: mice with prolonged spared nerve injury (SNI) ²¹, as well as Sham controls, received high doses of oxycodone for two weeks and, following three weeks of spontaneous withdrawal, mPFC, NAc and VTA tissues were collected for RNA Sequencing (RNA- Seq) analysis. Overall, this example highlights critical adaptations in mouse reward circuits associated with oxycodone physical dependence and reveals that chronic neuropathic pain states affect sensory, affective, and molecular signatures of opioid withdrawal. Guided by bioinformatic predictions from RNA-Seq analyses, the inventors demonstrate that treatment with the HDAC1/2 inhibitor RBC1HI alleviates mechanical allodynia and prevents the expression of sensory and affective manifestations of oxycodone withdrawal, pointing to a novel therapeutic approach for the management of chronic pain in opioid-dependent subjects. Example 1: Oxycodone withdrawal produces thermal hyperalgesia and mechanical allodynia in SNI and Sham groups of mice. [0174] A novel paradigm of oxycodone exposure was designed to assess sensory and affective-like behaviors associated with spontaneous oxycodone withdrawal in Sham mice, as well as in mice with prolonged peripheral nerve injury (FIG.1A, FIG.13A). Sensory hypersensitivity was monitored in long–term SNI and Sham groups of male mice with or without prolonged oxycodone exposure, followed by spontaneous drug withdrawal. Over ten weeks, changes in body weight during oxycodone exposure and spontaneous withdrawal were assessed. No significant changes in weight were observed in long-term SNI (SNI-Sal) groups compared to Sham Saline (Sham-Sal) controls. However, the weights of SNI and Sham mice receiving chronic oxycodone injections (SNI-Oxy and Sham-Oxy, respectively) were significantly altered as compared with Sham-Sal and SNI-Sal controls. Sham-Oxy and SNI-Oxy groups both showed decreased weights compared to Sham-Sal animals two d into oxycodone treatment. In addition, SNI- Oxy animals exhibited a unique weight loss 4 d into withdrawal (repeated measures two- way ANOVA; time x treatment, interaction F30,480 =6.653, p<0.0001; Tukey’s multiple comparisons Sham-Oxy vs Sham-Sal OD2 q=6.029, df=528, p=0.0001; SNI-Oxy vs Sham-Sal OD2 q=4.131, df=528, p=0.019, WD4 q=3.784, df=528, p=0.0384) (FIG. 13B). The most notable weight decrease was observed during the first two d of oxycodone administration for both SNI-Oxy and Sham-Oxy groups. The effect of oxycodone withdrawal on weight loss was significant between SNI and sham groups throughout the withdrawal monitoring period. SNI-Oxy mice demonstrated significant weight loss that persisted up to 8 d after oxycodone cessation. Both SNI-Oxy and Sham- Oxy groups normalized their weight change by 17 d of drug withdrawal (FIG.13B). [0175] The impact of chronic oxycodone administration on long-term mechanical allodynia associated with SNI was monitored. Significant alleviation of mechanical allodynia at 13 d of oxycodone treatment was observed when mice were tested five h after oxycodone injection (F_3,108 = 17.22, P=0.0001) (FIG.1C). In a separate cohort of mice, mechanical allodynia at 16 h post oxycodone injection at day 13 was monitored. At this time point after drug injection, SNI-Oxy mice showed significant improvement from mechanical allodynia while the Sham Oxy group demonstrated mechanical hypersensitivity , reflecting opioid-induced hyperalgesic states (two-way ANOVA; treatment x time, F24,279=20.87, P<0.001) (FIG.1D). During spontaneous withdrawal, Sham-Oxy mice displayed significant mechanical hyperalgesia up to 14 d after oxycodone treatment discontinuation, whereas SNI mice returned to untreated, post-injury Von Frey thresholds (FIG.1D). [0176] Thermal hypersensitivity was monitored using the Hargreaves assay. SNI-Oxy mice developed thermal hyperalgesia after 5 d of oxycodone injection, which was also observed on day 10 (repeated measures two-way ANOVA interaction F21,217=8.826, p<0.0001; Tukey’s m.c. SNI-Oxy vs Sham-Sal OD5 q=10.53, df=248, p<0.0001, OD10 q=11.64, df=248, p<0.0001) (FIG. 1E). Sham-Oxy groups showed no opioid-induced thermal hyperalgesia during the two-week period (e.g., 14 days) of drug treatment; however, these animals displayed persistent and significant hyperalgesia at 4 d after (up to 7) the induction of spontaneous withdrawal (two-way ANOVA; time x treatment, F=_21,217 =8.826, P<0.0001) (FIG.1E). Overall, these findings suggest that chronic neuropathic pain states exacerbate symptoms of chronic oxycodone exposure.(Tukey’s m.c. Sham-Oxy vs. Sham-Sal WD4 q=8.943, df=248, p<0.0001) (FIG.13C). This effect was also observed with the SNI-Oxy group (Tukey’s m.c. SNI-Oxy vs Sham-Sal WD4 q=12.63, df=248, p<0.0001). [0177] The impact of chronic oxycodone administration on long-term mechanical allodynia associated with SNI was monitored next. SNI reliably induced mechanical hypersensitivity through 49 d post-surgery (repeated measures two-way ANOVA interaction F24,248=20.75, p<0.0001; Tukey’s m.c. SNI-Oxy pre-treatment d 7-49 p<0.0001). Mechanical allodynia was monitored at 16 h post oxycodone injection at day 13 of drug treatment. At this time point after drug injection, SNI-Oxy mice showed significant, but partial, improvement from mechanical allodynia compared to pre- treatment SNI thresholds (Tukey’s m.c. OD13 SNI-Oxy vs Sham-Sal q=4.07, df=279, p=0.0223; SNI-Oxy vs SNI-Sal q=14.65, df=279, p<0.0001), while the Sham-Oxy group demonstrated lower mechanical thresholds compared to all time points before Oxy treatment (Tukey’s m.c. Sham-Oxy vs Sham-Sal OD13 q=5.003, df=279, p=0.0027) (FIG.1, FIG.13). During spontaneous withdrawal, it was observed a persistent mechanical hypersensitivity in Sham-Oxy mice at 7 and 14 d after oxycodone treatment discontinuation (Tukey’s m.c. Sham-Oxy vs Sham-Sal WD7 q=5.42, df=279, p=0.0009, WD14 q=3.961, df=279, p=0.0278), whereas mice from the SNI-Oxy group returned to Von Frey thresholds observed before drug treatment (FIG 1, FIG.13). Significant , but partial, alleviation of mechanical allodynia was obseved at 13 d of oxycodone treatment in a separate SNI-Oxy group, when tested in mice 5 h after oxycodone injection (F3,54=16.22, p<0.0001; Sidak’s m.c. SNI-Sal vs Sham-Sal t=8.717, df=108, p<0.0001; SNI-Oxy vs SNI-Sal t=5.897, df=108, p<0.0001) (FIG 1, FIG.13). Overall, these findings suggest that chronic neuropathic pain states exacerbate symptoms of chronic oxycodone exposure, particularly during active treatment. Example 2: Oxycodone withdrawal produces deficits in social and emotional behavior. [0178] A battery of behavioral paradigms were used to evaluate the impact of neuropathic pain states on emotional and motivational manifestations of chronic oxycodone administration and subsequent withdrawal (FIG.14A). Peripheral nerve injury significantly affected the time spent on the bright side of the dark-light box 5 d after withdrawal. The percentage time spent on the light compartment was significantly reduced—a pro-anxiety-like effect—in SNI-Sal compared to Sham-Sal (two-way ANOVA interaction F_1,46=0.1312, p=0.7189; Sidak’s m.c. t=2.387, df=46, p=0.0418), and in SNI-Oxy compared to Sham-Oxy (Sidak’s m.c. t=2.696, df=46, p=0.0195) (FIG.14B). Next the marble burying assay was used to further assess anxiety-like behaviors, which in mice generally manifests as more marbles buried. On Day 9 after spontaneous oxycodone withdrawal, SNI-Oxy mice buried significantly fewer marbles than Sham-Oxy groups (two-way ANOVA; interaction, F1,45 =17.89, P=0.0001; Sidak’s m.c. t=3.068, df=45, p=0.0073) (FIG.14C). Furthermore, as expected, SNI-Sal animals buried more than their Sham-Sal counterparts (Sidak’s m.c. t=2.912, df=45, p=0.0111). Interestingly, Sham-Oxy animals buried substantially more marbles than Sham-Sal animals (Sidak’s m.c. t=4.476, df=45, p=0.0001) reinforcing the induction of anxiety-like states during spontaneous withdrawal alone. While at face value these findings would suggest SNI-Oxy induces lower levels of anxiety, the combination of the two perturbations might be interpreted as a reduced capacity to address environmental stressors, thus representing maladaptive indifference to these stressors. Voluntary running wheel activity, which is considered a measure of anxiety and motivation, revealed similar results as marble burying, whereby Sham-Oxy animals ran significantly more than SNI-Oxy counterparts (two-way ANOVA interaction F_1,29=10.33, p=0.0032; Sidak’s m.c. t=3.38, df=29, p=0.0042), suggesting high anxiety levels without nerve injury and decreased capacity with injury under withdrawal (FIG.14D). A strong trend was observed between SNI-Oxy and SNI-Sal, further suggesting reduced capacity beyond injury-induced effects (Sidak’s m.c. t=2.238, df=29, p=00651) and a trend upwards between Sham Oxy and Sham-Sal that reinforces withdrawal-induced anxiety states (Sidak’s m.c. t=2.31, df=29, p=0.0557). Next sociability was assessed, using the two-choice preference model²⁶. The test was performed 12 d after withdrawal. All groups, regardless of peripheral nerve injury or oxycodone exposure, showed no preference for either of the empty cages during the habituation phase of this test (FIG.14E). In the sociability test, Sham-Sal and Sham-Oxy (Sham two-way ANOVA interaction F1,56=0.01304, p=0.9095; Sidak’s m.c. Sham-Sal t=2.839, df=56, p=0.0126; Sham-Oxy t=2.331, df=56, p=0.0462), as well as SNI-Sal (SNI two-way ANOVA interaction F1,58=9.51, p=0.0031; Sidak’s m.c. SNI-Sal t=4.489, df=58) displayed preference for a social target, while SNI-Oxy mice showed no preference for a social target vs an empty cage (FIG.14F). [0179] A battery of affective behavioral paradigms were used to evaluate the impact of neuropathic pain states on emotional and motivational manifestations of chronic oxycodone administration (FIG.2A). -A suppressed feeding (NSF) assay was subsequently conducted, which revealed abnormal behavioral responses after 15 d of oxycodone withdrawal As shown in FIG.2E-and FIG.14G, at Day 15 of oxycodone withdrawal, SNI-Oxy, SNI-Sal, and Sham-Oxy groups showed increased latency to eat in a novel environment compared to Sham-Sal animals, which is interpreted as an increase in anxiety- and depression-related behavior (two-way ANOVA; interaction, F1,56= 6.052, p=0.0170) (FIG.2D), which is interpreted as an increase in anxiety-related behavior (Sidak’s m.c. SNI-Sal vs Sham-Sal t=2.963, df=56, p=0.0089; Sham-Oxy vs Sham-Sal t=3.249, df=56, p=0.0039; Tukey’s m.c. SNI-Oxy vs Sham-Sal q=3.92, df=56, p=0.0369) (FIG.14G). Home cage latency to eat decreased in the Sham-Oxy group compared to Sham-Sal (two-way ANOVA; interaction, F1,62= 1.841, P=0.1797; Sidak’s m.c. Sham- Oxy vs Sham-Sal t=2.843, df=62, p=0.012) (FIG.2E and FIG.14H). Total distance traveled in a novel arena was significantly decreased by oxycodone withdrawal regardless of neuropathic pain state (two-way ANOVA; treatment, F1,48= 20.45, P<0.001; Sidak’s m.c. Sham-Oxy vs Sham-Sal t=2.88, df=48, p=0.0118; SNI-Oxy vs SNI-Sal t=3.505, df=48, p=0.002) (FIG.14I). [0180] Peripheral nerve injury significantly affected the time spent on the bright side of the dark-light box. The percentage time spent on the light compartment was significantly reduced—a pro-anxiety-like effect—in SNI-Oxy compared to Sham-Sal, and in SNI-Oxy compared to Sham-Oxy and a trend towards significance in SNI-Sal compared to Sham- Sal (p<0.09) (two-way ANOVA; PNI effect, F1,45 =11.64, P=0.0014) (FIG.14G). The combination of oxycodone withdrawal and SNI not only promoted anxiety-like behaviors but also induced photophobia²², a common symptom of opioid withdrawal. [0181] Next, the marble burying assay was used to further assess anxiety-like behaviors. Sham-Oxy and SNI-Sal mice buried significantly more marbles—a pro-anxiety-like effect—compared to Sham-Sal mice. SNI-Oxy mice buried significantly fewer marbles than Sham-Oxy groups (two-way ANOVA; interaction, F1,45 =17.89, P=0.0001) (FIG. 2H). While at face value this would suggest SNI-Oxy induces lower levels of anxiety, the combination of the two perturbations might be interpreted as a reduced capacity to address environmental stressors, instead showing maladaptive indifference to these stressors. [0182] Although no significant changes in the open field assay were seen (FIG.20A), a significant increase was observed in the total time spent in the open arm with SNI-Oxy compared to the Sham-Oxy group in the elevated plus maze (EPM) assay (two-way ANOVA interaction F_1,31=6.299, p=0.0175; Sidak’s m.c. Oxy SNI vs Sham t=3.62, df=31, p=0.0021) (FIG.20B). No difference was observed between groups in the nesting assay (FIG.9). In the voluntary running wheel assay of motivation, the combination of chronic pain and oxycodone withdrawal led to a reduction in cycles run as opposed to an increase seen in Sham-Oxy mice. This observation further supports an SNI-dependent reduction in motivation in groups of mice experiencing withdrawal, as opposed to a purely anxiety-like phenotype observed in pain-free oxycodone withdrawing mice (two- way ANOVA; Interaction, F_1,29 =10.33, P=0.0032) (FIG.20C). [0183] Finally, the SNI-Oxy group was primed for locomotor activation in response to a low oxycodone dose (1mg/kg. s.c) at 18 d of drug abstinence in SNI and sham mice (two-way ANOVA; Interaction, F_1,29 =10.33, P=0.0032) (FIG.2J and FIG.2K). FIG.14J and FIG.14K shows locomotor activity at 110 min (two-way ANOVA; interaction, F1,25 =0.3945, p=0.3945; Sidak’s m.c. SNI-Oxy vs SNI-Sal t=2.486, df=25, p=0.0395). Furthermore, the SNI-Oxy condition led to a substantial reduction in locomotion, which was interpreted as neuropathic-withdrawal-associated exhaustion, by minute 180 (FIG. 14L) (two-way ANOVA interaction, F1,25=5.842, p=0.0233; Sidak’s m.c. SNI-Oxy vs SNI-Sal t=2.959, df=25, p=0.0133). Together, these findings reveal that chronic exposure to oxycodone under prolonged nerve injury states leads to more severe physical and affective manifestations of drug withdrawal. Example 3: Oxycodone withdrawal in long-term SNI and Sham states triggers broad transcriptomic patterns in the brain’s reward circuitry. [0184] Tissues were collected after mice had undergone 2.5 months of peripheral nerve injury and 21 d of oxycodone withdrawal and were then processed for RNA-seq (FIG. 3A). Differential expression analysis was performed against the Sham-Sal control condition for SNI-Sal, Sham-Oxy, and SNI-Oxy cohorts across all relevant brain regions. In several cases, region-specific alterations in transcriptional profiles were observed. The combination of oxycodone withdrawal and SNI altered a total of 1012 genes in the NAc (nominal p<0.05, log2FC>|0.5|), where 708 showed upregulation and 305 showed downregulation. In the mPFC, 1115 genes were differentially regulated (566 upregulated and 549 downregulated). Out of 430 differentially expressed genes (DEG) in the VTA, 228 were upregulated and 202 were downregulated compared to Sham-Sal controls. SNI- Sal triggered a total of 579 DEGs in the NAc (263 up, 316 down), 1058 DEGs in the mPFC (708 up, 350 down), and 533 DEGs in the VTA (249 up, 284 down) as compared to Sham-Sal controls. Oxycodone withdrawal in sham mice altered ~2620 genes in the NAc (1759 up, 871 down), 1455 genes in the mPFC (649 up, 806 down), and 564 genes in the VTA (336 up, 228 down) as compared to Sham-Sal controls (Table 2). [0185] The next goal was to understand the transcriptional changes that correlate long-term peripheral nerve injury with oxycodone withdrawal in three brain regions implicated in chronic pain and opioid dependence: the NAc, mPFC and VTA. Tissues were collected from mice after 2.5 months of peripheral nerve injury, 14 d of oxycodone administration, and 21 d of spontaneous withdrawal, and were then processed for RNA-Seq (FIG.15A). Differential expression analysis showed region-specific alterations in transcriptional profiles. The combination of SNI-Oxy vs Sham-Sal altered the expression of a total of 1012 genes in the NAc, 1116 genes in the mPFC, and 533 genes in the VTA (FIG.15B, FIG.15 E, and FIG.15H; nominal p<0.05, log2FC≥|0.5|). SNI-Sal triggered a total of 1457 DEGs in the NAc, 1052 DEGs in the mPFC, and 425 DEGs in the VTA as compared to Sham-Sal controls (FIG.15B, FIG.15E, and FIG.15H). The Sham-Oxy condition altered 2609 genes in the NAc, 1449 genes in the mPFC, and 584 genes in the VTA as compared to Sham-Sal controls (FIG.15B, FIG.15E, and FIG.15H). [0186] Table 1. Comparison of IPA Top Canonical Pathways in mPFC, NAc, and VTA tissues from SNI-Oxy and SNI-Sal animals. Differentially expressed genes underlying each pathway are bolded if they are conserved across brain regions within the same pathway

[0187] Table 2. Total number of Differentially Expressed Genes (DEGs) across comparisons and reward related brain regions 0.5< log-2 fold<-0.5, p<0.05.

[0188] In some embodiments, there were 420, 191, and 59 DEGs that overlapped between Sham-Oxy, SNI-Sal, and SNI-Oxy in the NAc, mPFC and VTA, respectively (FIG. 3B, FIG. 3E, and FIG. 3H), suggesting that neuropathic pain/opioid withdrawal trigger more transcriptomic adaptations in the NAc [0189] In some embodiments, there were 420, 192, and 19 DEGs that overlapped between Sham-Oxy, SNI-Sal, and SNI-Oxy in the NAc, mPFC and VTA, respectively (FIG. 15B, FIG. 15 E, and FIG. 15H), suggesting a prominent role of the NAc in states of pain and opioid withdrawal with/without nerve injury. [0190] The highest number of DEGs was observed in the Sham-Oxy condition across all brain regions. Union heat maps sorted by log-fold change (LFC), and compared with DEGs that were changed as a result of SNI (SNI-Sal vs Sham-Sal), showed a similar pattern of expression across oxycodone withdrawal conditions compared to Sham-Sal controls (FIG. 3C, FIG. 3F, FIG. 3I, FIG. 15C, FIG. 15F, and FIG.15I). Within the NAc and mPFC, the pattern of gene expression between Sham-Oxy vs Sham-Sal and SNI-Oxy vs Sham-Sal comparisons, albeit with fewer genes affected by oxycodone withdrawal under SNI (FIG.3C, FIG.3F, FIG.15C and FIG.15F). In the VTA, several genes were oppositely regulated between SNI-Oxy, SNI-Sal, and Sham-Oxy. [0191] Next, these data analyses were complemented with a two-sided rank-rank hypergeometric overlap (RRHO) analysis to identify patterns and strengths of transcriptome-wide overlap in a threshold-free manner. RRHO analysis confirmed similar directional regulation of genes by oxycodone withdrawal in SNI and Sham groups of mice (FIG.3D, FIG.3G, FIG.3J, left and FIG.15D, FIG.15G, FIG.15J) across all surveyed brain regions (NAc, mPFC, and VTA). RRHO plots also revealed that the SNI- Oxy condition induced a unique transcriptional signature compared to the Sham-Oxy condition in the NAc and mPFC, but not in the VTA (FIG.3D, FIG.3G, FIG.3J, right and FIG.15D, FIG.15G, FIG.15J). These data suggest that oxycodone withdrawal promotes broad transcriptional alterations under prolonged pain states that are unique for each brain region. [0192] To better understand the molecular signature of DEGs affected by oxycodone withdrawal under SNI vs Sham conditions, a gene ontology (GO) analysis was performed for enriched biological processes and Ingenuity Pathway Analysis (IPA). There was a significant DEG overlap between the SNI-Oxy vs SNI-Sal and Sham-Oxy vs Sham-Sal conditions in the NAc and mPFC (105 and 106, respectively) (FIG.16A and FIG.16D). However, Oxy withdrawal caused substantially different transcriptomic profiles in nerve- injured groups compared to sham groups. Only 21 co-expressed DEGs between SNI-Oxy vs SNI-Sal and Sham-Oxy vs Sham-Sal were observed in the VTA (FIG.16G). FIGs. 16A,D show union heat maps of DEGs that are shared between the comparisons above, interestingly demonstrating opposite directional regulation of these genes in the NAc as opposed to unidirectional regulation in the mPFC. FIG.16G shows that shared DEGs between these conditions in the VTA did not have a clear directionality of regulation. Also, as seen in FIGs.16A,D-manuscript, gene ontology analysis of DEGs conserved between these treatment conditions in the NAc was associated with neuronal morphology, cAMP signaling, and alcohol abuse, whereas in the mPFC, glutamate reception was a top hit. Of note, this analysis, which highlights the consistent effects of oxycodone withdrawal across injury states, was limited due to the few DEGs available when comparing these conditions. In the VTA (FIG.16G), ADH1 and LRG1 appeared as conserved targets for predicted drug treatments [0193] Top predicted upstream regulators (URs) of transcriptional signatures were distinctly altered in several brain regions by oxycodone withdrawal in neuropathic as well as in Sham states. Within the NAc for the Sham-Oxy vs Sham-Sal comparison, FEV, SETDB1, DTNBP1 and COLQ were predicted URs (FIG.16B), while in SNI-Oxy vs SNI-Sal comparisons, SIRT3, LRPPRC, and EOMES appeared (FIG.16C). The lack of overlap between top predicted URs emphasizes the distinct transcriptomic effects of Oxy in nerve-injured vs uninjured conditions. However, URs from both regions are implicated in epigenetic/transcriptional maintenance of the neuronal life cycle, such as FEV, SETDB1, and SIRT3. In the mPFC, ADCYAP1 and HTT were predicted URs affected in the Sham- Oxy vs Sham-Sal condition (FIG.16E), while MAPK3, CREB1, and MEF2D, key regulators of activity in adult neurons, were implicated in the SNI-Oxy vs SNI-Sal comparison (FIG.16F). Lastly, in the VTA, SOCS1 and CGAS were implicated in the Sham-Oxy vs Sham-Sal comparison (FIG.16H), suggesting the engagement of interferon-related pathways by Oxy withdrawal alone, while in the SNI-Oxy vs SNI-Sal comparison, URs such as RELA, STAT3, and ELK3 were predicted (FIG.16I), which play a more important role in neuronal survival. Pathway analysis highlighting the effect of pain across the NAc, mPFC and VTA is shown in FIG.21B, FIG.21 D, and FIG. 21F. [0194] Next a IPA canonical pathway analysis was performed for the SNI-Oxy vs SNI-Sal comparison in the NAc, mPFC, and VTA to better assess the molecular mechanisms affected by DEGs associated with withdrawal states under neuropathic pain. As seen in Table 1, conserved pathways across these brain regions included CREB signaling in neurons, GPCR signaling, circadian rhythm signaling, and osteoarthritis pathways Example 4: Oxycodone withdrawal in long-term SNI and Sham states triggers broad transcriptomic patterns in the brain’s reward circuitry. [0195] Gene ontology (GO) analysis for enriched biological processes and Ingenuity Pathway Analysis (IPA) was performed to better understand the molecular signature of DEGs affected by oxycodone withdrawal under peripheral nerve injury versus sham conditions. There was a significant overlap (>550 DEGs) between oxycodone withdrawal in long-term SNI and pain-free states in the NAc and mPFC (FIG.4A and FIG.4G). Very few co-expressed DEGs between oxycodone withdrawal in SNI and sham groups were observed in the VTA (FIG.4M). FIGs.4B and 4H show Union heat maps of co- regulated DEGs with long–term SNI in the NAc and mPFC. FIG.4N shows that DEGs which overlapped between oxycodone withdrawal in SNI and sham in the VTA were oppositely regulated. [0196] Complementary analysis to assess the effect of oxycodone withdrawal in SNI versus sham groups was performed in the NAc, mPFC and VTA. DAVID functional annotation for gene ontology was used for biological processes and Ingenuity Pathway Analysis (IPA) was used to identify Upstream Regulators. These analyses were performed independent of the direction of gene expression change. The top gene ontology terms for oxycodone withdrawal in sham groups where vastly different across brain regions. In the NAc, significant ontologies include cell adhesion, axon guidance, nervous system development, and chemical synaptic transmission (for all ontologies p<0.0030) (FIG. 4C). In the mPFC, significant ontologies included cell adhesion, collagen fibril organization, negative regulation of megakeratinocyte differentiation, and protein heterotetramerization (FIG.4I). VTA enriched ontologies included multicellular organism development, neuron differentiation, neuropeptide signaling pathway, and embryonic limb morphogenesis (FIG.4O). [0197] Transcriptional changes that correlate long-term peripheral nerve injury with oxycodone withdrawal in three brain regions implicated in chronic pain and opioid dependence were evaluated (the NAc, mPFC and VTA). Tissues were collected from mice after 2.5 months of peripheral nerve injury, 14 d of oxycodone administration, and 21 d of spontaneous withdrawal, and were then processed for RNA-Seq (FIG.15A). Differential expression analysis showed region-specific alterations in transcriptional profiles. The combination of SNI-Oxy vs Sham-Sal altered the expression of a total of 1012 genes in the NAc, 1116 genes in the mPFC, and 533 genes in the VTA (Figure 3B, E, H-man; nominal p<0.05, log₂FC≥|0.5|). SNI-Sal triggered a total of 1457 DEGs in the NAc, 1052 DEGs in the mPFC, and 425 DEGs in the VTA as compared to Sham-Sal controls (Figure 3B, E, H-man). The Sham-Oxy condition altered 2609 genes in the NAc, 1449 genes in the mPFC, and 584 genes in the VTA as compared to Sham-Sal controls (Figure 3B, E, H-man). [0198] There were 420, 192, and 19 DEGs that overlapped between Sham-Oxy, SNI-Sal, and SNI-Oxy in the NAc, mPFC and VTA, respectively (FIG.15B, FIG.15E, and FIG. 15H), suggesting a prominent role of the NAc in states of pain and opioid withdrawal with/without nerve injury. The highest number of DEGs was observed in the Sham-Oxy condition across all brain regions. Union heat maps sorted by log-fold change (LFC), and compared with DEGs that were changed as a result of SNI (SNI-Sal vs Sham-Sal), showed a similar pattern of expression across oxycodone withdrawal conditions compared to Sham-Sal controls (FIG.15C, FIG.15F, and FIG.15I). Within the NAc and mPFC, the pattern of gene expression between Sham-Oxy vs Sham-Sal and SNI-Oxy vs Sham-Sal comparisons, albeit with fewer genes affected by oxycodone withdrawal under SNI (FIG.15C and FIG.15F). In the VTA, several genes were oppositely regulated between SNI-Oxy, SNI-Sal, and Sham-Oxy. [0199] Next this data was analyzed with a two-sided rank-rank hypergeometric overlap (RRHO) analysis to identify patterns and strengths of transcriptome-wide overlap in a threshold-free manner. RRHO analysis confirmed similar directional regulation of genes by oxycodone withdrawal in SNI and Sham groups of mice (FIG.15D, FIG.15G, and FIG.15J, left) across all surveyed brain regions (NAc, mPFC, and VTA). RRHO plots also revealed that the SNI-Oxy condition induced a unique transcriptional signature compared to the Sham-Oxy condition in the NAc and mPFC, but not in the VTA (FIG. 15D, FIG.15G, FIG.15J, right). These data suggest that oxycodone withdrawal promotes broad transcriptional alterations under prolonged pain states that are unique for each brain region. [0200] To better understand the molecular signature of DEGs affected by oxycodone withdrawal under SNI vs Sham conditions ,a gene ontology (GO) analysis was performed for enriched biological processes and Ingenuity Pathway Analysis (IPA). There was a significant DEG overlap between the SNI-Oxy vs SNI-Sal and Sham-Oxy vs Sham-Sal conditions in the NAc and mPFC (105 and 106, respectively) (FIG.16A and FIG.16D). However, Oxy withdrawal caused substantially different transcriptomic profiles in nerve- injured groups compared to sham groups. Only 21 co-expressed DEGs between SNI-Oxy vs SNI-Sal and Sham-Oxy vs Sham-Sal were observed in the VTA (FIG.16G). FIGs. 16A,D show union heat maps of DEGs that are shared between the comparisons above, interestingly demonstrating opposite directional regulation of these genes in the NAc as opposed to unidirectional regulation in the mPFC. FIG.16G shows that shared DEGs between these conditions in the VTA did not have a clear directionality of regulation. Also, as seen in FIG.16A,D, gene ontology analysis of DEGs conserved between these treatment conditions in the NAc was associated with neuronal morphology, cAMP signaling, and alcohol abuse, whereas in the mPFC, glutamate reception was a top hit. Of note, this analysis, which highlights the consistent effects of oxycodone withdrawal across injury states, was limited due to the few DEGs available when comparing these conditions. In the VTA (FIG.16G), ADH1 and LRG1 appeared as conserved targets for predicted drug treatments. [0201] The combination of oxycodone withdrawal with SNI altered distinct ontologies compared to oxycodone withdrawal in sham groups. Ontologies affected across brain regions were mostly unique. In the NAc, several ontologies were shared between oxycodone withdrawal in SNI versus sham including cell adhesion, nervous system development, and chemical synaptic transmission (red) (FIG.4E). In the mPFC, enriched gene ontologies included cilium movement, regulation of transmembrane transport, and potassium ion (FIG.4). In the VTA, enriched ontologies included cellular response to tumor necrosis factor, cellular response to interferon-gamma, and inner ear morphogenesis (FIG.4Q). Cell adhesion was enriched in oxycodone withdrawal alone as well as in oxycodone withdrawal with peripheral nerve injury in the NAc and mPFC. The gene ontologies affected by peripheral nerve injury in the NAc include cAMP-mediated signaling and ion transport (FIG.10A). In the mPFC the ontologies include cell-cell signaling and cilium movement and in the VTA the enriched ontologies include immune response and response to interferon- gamma/beta (FIG.10C and 10E) Together, these results suggest that oxycodone exposure and chronic pain states induces unique, long- lasting changes in different reward related-brain regions. [0202] Top predicted upstream regulators (URs) of transcriptional signatures were distinctly altered in several brain regions by oxycodone withdrawal in neuropathic as well as in Sham states. Within the NAc for the Sham-Oxy vs Sham-Sal comparison, FEV, SETDB1, DTNBP1 and COLQ were predicted URs (FIG.16B), while in SNI-Oxy vs SNI-Sal comparisons, SIRT3, LRPPRC, and EOMES appeared (FIG.4D, FIG.4E, and FIG.16C).The lack of overlap between top predicted URs emphasizes the distinct transcriptomic effects of Oxy in nerve-injured vs uninjured conditions. However, URs from both regions are implicated in epigenetic/transcriptional maintenance of the neuronal life cycle, such as FEV, SETDB1, and SIRT3. In the mPFC, ADCYAP1 and HTT were predicted URs affected in the Sham-Oxy vs Sham-Sal condition (FIG.16E), while MAPK3, CREB1, and MEF2D, key regulators of activity in adult neurons, were implicated in the SNI-Oxy vs SNI-Sal comparison (FIG.16F). Lastly, in the VTA, SOCS1 and CGAS were implicated in the Sham-Oxy vs Sham-Sal comparison (FIG. 16H), suggesting the engagement of interferon-related pathways by Oxy withdrawal alone, while in the SNI-Oxy vs SNI-Sal comparison, URs such as RELA, STAT3, and ELK3 were predicted (FIG 16I) which play a more important role in neuronal survival. Pathway analysis highlighting the effect of pain across the NAc, mPFC and VTA is shown in FIG.2B, FIG.2D, FIG.2F, FIG.21B, FIG.21D, and FIG.21F. [0203] An IPA canonical pathway analysis was also performed for the SNI-Oxy vs SNI-Sal comparison in the NAc, mPFC, and VTA to better assess the molecular mechanisms affected by DEGs associated with withdrawal states under neuropathic pain. As seen in Table 1, conserved pathways across these brain regions included CREB signaling in neurons, GPCR signaling, circadian rhythm signaling, and osteoarthritis pathways Example 5: Oxycodone withdrawal induces distinct transcriptional regulation in NAc, mPFC, and VTA in pain-free vs neuropathic pain states. [0204] RRHO plots demonstrated correlation between various brain regions with oxycodone withdrawal in sham mice and in mice with chronic neuropathic pain. The NAc and mPFC showed high correlation in gene expression patterns and DEGs showed similar positive correlation with oxycodone withdrawal in sham mice (FIG.5A). However, with the combination of oxycodone withdrawal and peripheral nerve injury, this pattern of gene expression was negatively correlated between the NAc and mPFC (FIG.5B). The NAc and VTA showed a similar correlation in up- and down-regulated genes with the combination of peripheral nerve injury and opioid withdrawal. With the same combination of oxycodone withdrawal and peripheral nerve injury, the VTA and mPFC showed opposite regulation of DEGs: genes that were upregulated in the mPFC were downregulated across the VTA and vice versa (FIG.5B). [0205] Next, canonical pathways that are affected across brain regions by oxycodone withdrawal in sham versus long-term SNI mice were identified. Several top canonical pathways were significantly upregulated in the NAc of mice undergoing oxycodone withdrawal with peripheral injury as compared to animals without peripheral nerve injury. These pathways include synaptogenesis signaling pathway, CREB signaling in neurons, dopamine-DARPP32 feedback pathway, calcium signaling, protein kinase A signaling, and opioid signaling. In the mPFC, several canonical pathways were contra-regulated with oxycodone withdrawal with compared to without SNI. These include synaptic long- term depression pathways, dopamine-DARPP32 feedback, and opioid signaling pathways. Within the VTA, several canonical pathways were significantly regulated with oxycodone withdrawal selectively in pain-free or chronic pain states. The canonical pathways downregulated in Sham-Oxy mice included PKC epsilon signaling in T- lymphocytes, dendritic cell maturation, and neuropathic pain signaling. Conversely, pathways that were upregulated under chronic pain states included CREB signaling in neurons, opioid signaling pathway, calcium signaling, and dopamine-DARPP32 feedback pathways (FIG.5C). [0206] These analyses pointed to a particular role for HDAC1. Although Hdac1 mRNA expression was significantly regulated in the NAc and mPFC in oxycodone withdrawal in both SNI and pain-free states, the direction and magnitude of regulation was different between SNI and pain-free mice (FIG.5D). HDAC1 has been shown previously to be a top regulator for several genes implicated in drug dependence, addiction, and pain (Kennedy, P. J. et al. Nat Neurosci, 2013, 16, 434-440), e.g., Mef2c, Bdnf, and Sgk1, in the NAc of Sham-Oxy mice (FIG.5E). In the mPFC, HDAC1 was shown to regulate several genes that overlap between long-term pain and pain-free states during oxycodone withdrawal, such as Cd34, Sfrp1, and Egr1 (data not shown). [0207] Several genes were randomly selected across brain regions for validations of the RNA-seq dataset by RT-qPCR. Changes between SNI-Sal, SNI-Oxy, and Sham-Oxy groups of mice were compared with Sham-Sal control groups. Bdnf, and Serpini1 were validated in the NAc which showed opposite regulation with oxycodone withdrawal under long-term neuropathic pain compared to pain-free states. Several other genes demonstrated similar opposite regulation with oxycodone withdrawal in pain-free states compared to long-term neuropathic pain states, including Tph2, Wnt10a, Csfr2b in the mPFC, and Foxd3, c-Fos, Clip, and Itgad in the VTA (FIGs.6A-C). [0208] Despite differences in explicit DEGs, an RRHO analysis strategy enabled us to look at overall concordance or lack thereof in gene expression in a threshold-free manner. As seen in FIG.17A, when comparing Sham-Oxy vs Sham-Sal transcriptomic regulation across regions, the NAc and mPFC demonstrate high concordance, or similar directionality, of expression for the same genes. However, concordance is observed when comparing NAc or mPFC to VTA, suggesting a more unique response to Oxy withdrawal. Interestingly, when comparing SNI-Oxy to SNI-Sal transcriptomics across brain regions, the NAc and mPFC lose substantial concordance and instead display mild counter-regulation of the same genes. The NAc and VTA increased in concordance in terms of unidirectional regulation of the same genes, while the mPFC and VTA displayed concordance in the form of contra-directional regulation (FIG.17B). Altogether, this analysis demonstrates highly similar responses between the NAc and mPFC during withdrawal in an injury-free state, yet a stronger transcriptomic relationship between the NAc/mPFC and VTA during withdrawal in injured states. [0209] Next canonical pathways were identified that are affected across brain regions for the Sham-Oxy vs Sham-Sal, SNI-Oxy vs Sham-Sal, and SNI-Oxy vs SNI-Sal comparisons (FIG.17C). Interestingly, in the mPFC and NAc, most pathways that were implicated in the Sham-Oxy vs Sham-Sal and SNI-Oxy vs Sham-Sal were either much more mildly associated with or counter-regulated in the SNI-Oxy vs SNI-Sal condition, reinforcing the unique transcriptomic signature of oxycodone under nerve injury. One such pathway that is crucial for the regulation of activity in adult neurons is CREB Signaling in Neurons, which is uniquely downregulated in the NAc only in the SNI-Oxy vs SNI-Sal comparison. When this pathway is expanded (FIG.17D), inhibition of several cytoplasmic regulators of CREB activity was predicted to regulate and further contribute to the observed downregulation of CREB and G protein signaling-related transcript isoforms. However, several top canonical pathways were conserved, yet directionally counter-regulated between the mPFC/VTA and NAc under Sham-Oxy vs Sham-Sal and SNI-Oxy vs Sham-Sal comparisons. These included synaptogenesis signaling pathway, CREB signaling in neurons, estrogen receptor signaling, and G protein-coupled receptor signaling. [0210] Top predicted URs were also identified across the aforementioned comparisons in the mPFC, NAc, and VTA. Several previously well-defined regulators of transcription were identified, including CREB1, TGFB1, BDNF, and NF ^B. However, in searching for a transcriptional regulator that has been less well defined in the cortico-mesolimbic system under neuropathic or withdrawal states, the upstream analysis pointed to a particular role for HDAC1. While not implicated in the VTA, HDAC1 was predicted to be upregulated across comparisons in the mPFC, while also being predicted to be affected in NAc by SNI-Oxy states (FIG.17E). In the mPFC, SNI-Oxy vs Sham-Sal comparisons suggest an increase in HDAC1 activity, with transcripts associated with the extracellular matrix (Col1A1, Col2a1, Col9a1) and transcriptional regulation (Myc, Egr1), undergoing gene expression changes that are concordant with published findings^28,29,30 (FIG.17F). In the NAc of Sham-Oxy mice, differential expression was observed for several genes implicated in drug dependence, addiction, and pain, such as Mef2c, Bdnf, and Sgk1^{31, 32,} 33, 34 all of which are HDAC1 targets, based on IPA upstream regulators predictions. [0211] Protein expression of HDAC1 in cells of the mPFC and NAc was verified (FIG.22A and FIG.22B), followed by RNAscope in situ hybridization to demonstrate co- localization of Hdac1 transcript with common neuronal and microglial transcripts (FIG. 22C and FIG 22F) Example 6: A novel HDAC1/2 inhibitor reverses mechanical hypersensitivity and thermal hyperalgesia associated with chronic oxycodone exposure. [0212] As HDAC1 is an upstream regulator in the NAc and mPFC from Sham-Oxy and SNI- Oxy mice, inhibition of this protein was hypothesized to alleviate associated behavioral abnormalities. Compound A (also referred to as “RCY1305” or “ACY1305”) was used which is a specific HDAC1/2 inhibitor that penetrates the brain upon systemic administration (FIG.12B). Information on the pharmacokinetic profiling of Compound A is shown in FIG.12A-C. Compound A showed great brain to plasma ratios and increased selectivity for HDAC1 compared to HDAC2 and HDAC3 after IP injection (FIG.12C). Using the SNI model, it was observed that daily treatment with Compound A (3 mg/kg i.p.) partially reversed mechanical allodynia (9 weeks) F_3,8 = 3.657, P = 0.0633 (FIG. 7B). In this oxycodone protocol, concurrent daily treatment of oxycodone and Compound A (3 mg/kg i.p.) prevented the development of thermal hyperalgesia associated with chronic oxycodone exposure in SNI mice F_6,87 = 6.334, P<0.0001). Furthermore, daily treatment with oxycodone along with Compound A prevented the development of thermal hyperalgesia during spontaneous withdrawal from oxycodone in both pain-free and SNI groups (FIGs.7C, D). Similar to the observations with male groups of mice, Compound A prevented the development of oxycodone-induced thermal hyperalgesia in female animals as well (FIG.7E). [0213] As the Class I HDAC1 is a predicted upstream regulator of oxycodone withdrawal under injured and uninjured states in the NAc and mPFC, it was hypothesized that inhibition of the deacetylase activity of HDAC1 might alleviate associated behavioral abnormalities. To test this hypothesis, a HDAC1/2 inhibitor, RBC1HI (FIG.23A,B) was utilized. Class I HDACs comprise HDAC 1, 2, 3, and the evolutionarily more distant HDAC8³⁵. HDACs 1, 2, and 3 function as components of corepressor complexes that widely regulate gene transcription, while the role of the more distantly related HDAC8 in transcription is not clear. Of particular interest for the isoform-selective pharmacological interrogation of HDAC1-3 are ortho-aminoanilide-derived small molecule inhibitors³⁶. The novel inhibitor RBC1HI was identified in enzymatic assays performed with recombinant proteins as a potent inhibitor that showed a dose-dependent inhibition of class I HDACs, with highest specificity for HDAC1, followed by HDAC2, free HDAC3, and HDAC3 bound to NCOR2 (AUC one-way ANOVA: F3,8=191.1, p<0.0001; Tukey's m.c. HDAC1 vs HDAC2 q=11.55, df=8, p=0.0002; HDAC1 vs free HDAC3 q=17.22, df=8 p<00001; HDAC1 vs HDAC3/NCOR2 q=16.21, df=8, p<0.0001; HDAC2 vs free HDAC3 q=17.22, df=8, p<0.0001; HDAC2 vs HDAC3/NCOR2 q=16.21, df=8, p<0.0001) in enzymatic assays performed with recombinant proteins (FIG.23B). However, because HDAC isoform selectivity depends in part on the binding of HDACs to other co-repressor complex proteins, the true isoform specificity in any specific cell type is less well understood³⁷. As it was recently shown for the prototype HDAC1/2-selective benzamide-derived inhibitor Cpd-60, which potently targets free HDAC3, which following ligand binding, can associate with CoREST into a catalytic inactive complex³⁷We, therefore also evaluated the inhibitory activity of RBC1HI towards free HDAC3 and found only a modest increase in affinity, retaining high isoforms selectivity over HDAC1 and 2 (FIG.23B). Upon systemic administration, RBC1HI is rapidly cleared from the plasma but has a longer-lasting presence in brain parenchyma (FIGs. 23C,D), rendering the compound better tolerated for long-term studies than other Class I HDAC inhibitors such as entinostat³⁸ (MS-275). Injection of RCB1HI (3 mg/kg i.p.) does not promote rewarding effects in the conditioned placed preference assay, as is seen with morphine (6 mg/kg s.c.) (FIG.4E). Furthermore, RBC1HI does not impair ambulatory locomotor activity (FIG.23F). [0214] Using the SNI model, it was observed that daily treatment with RBC1HI (3 mg/kg i.p.) partially reversed mechanical allodynia in male mice when beginning treatment at 9 weeks post-op (r.m. two-way ANOVA interaction F6,58=5.858, p<0.0001; Tukey’s m.c. D20 SNI-Sal-Veh vs. SNI-Sal-RBC1HI q=5.12, df=87, p=0.0027) (FIG.18A). In the oxycodone protocol, concurrent daily treatment with oxycodone and RBC1HI (3 mg/kg i.p.) prevented the development of thermal hyperalgesia associated with chronic oxycodone exposure in male SNI groups of mice (r.m. two-way ANOVA Interaction F_28,232=5.01, p<0.0001; Tukey’s m.c. D10 SNI-Oxy-Veh vs SNI-Oxy-RBC1HI q=10.17, df=290, p<0.0001) (FIG.18B). Furthermore, daily treatment with RBC1HI along with oxycodone prevented the development of thermal hyperalgesia during spontaneous withdrawal from oxycodone in both Sham and SNI groups (Tukey’s m.c. WD3 Sham- Oxy-Veh vs Sham-Oxy-RBC1HI q=10.96, df=290, p<0.0001; WD3 SNI-Oxy-Veh vs SNI-Oxy-RBC1HI q=8.625, df=290, p<0.0001) (FIG.18B). [0215] Although the studies reported thus far were all performed in male mice, it was important to ascertain whether HDAC1/2 inhibition would exert similar therapeutic-like actions in female mice. Indeed, it was found that RBC1HII exhibited antiallodynic effects in SNI-Sal to those observed in SNI-Oxy female mice 5 hrs after drug administration (two way ANOVA interaction F₁₃₆=5269 p=00025; Sidak’s m.c. OD10 SNI-Sal-Veh vs SNI-Sal-RBC1HI t=3.112, df=36, p=0.0072; OD10 SNI-Sal-Veh vs SNI-Oxy-Veh t=3.589, df=36, p=0.002) (FIG.18C,D) and also prevented mechanical allodynia by Day 7 after spontaneous withdrawal (r.m. two-way ANOVA interaction F12,144=4.531, p<0.0001; Tukey’s m.c. WD7 SNI-Oxy-RBC1HI vs SNI-Oxy-Veh q=5.551, df=180, p=0.0007) (FIG.18C). RBC1HI had no effects on female Sham-Sal mechanical thresholds, yet interestingly it mitigated analgesia observed in Sham-Oxy animals at 5hrs post-administration (two-way ANOVA interaction F_1,34=5.269, p=0.028; Sidak’s m.c. OD10 Sham-Sal-Veh vs Sham-Oxy-Veh t=2.517, df=34, p=0.0332; OD10 Sham-Oxy- Veh vs Sham-Oxy-RBC1HI t=2.754, df=34, p=0.0187) (FIG.18E,F). Similar to the observations with male groups, adjuvant administration of RBC1HI with oxycodone in female mice prevented the development of thermal hypersensitivity by Day 3 after the onset of spontaneous withdrawal (r.m. two-way ANOVA interaction F3,36=4.573, p=0.0082; WD3 Tukey’s m.c. SNI-Oxy-Veh vs SNI-Oxy-RBC1HI q=7.742, df=72, p<0.0001) (FIG.18G). Thermal hyperalgesia was not observed at 16hrs post oxycodone injection in SNI-Oxy females in the Hargreaves assay. Therefore, thermal was also hypersensitivity assessed in a 42^oC hot plate assay and observed lower hot plate thresholds at Day 12 of active drug administration in SNI-Oxy animals that was reversed by RBC1HI in a trending fashion (two-way ANOVA interaction F1,36=1.974, p=0.1686; Sidak’s m.c. OD12 SNI-Sal-Veh vs SNI-Oxy-Veh t=2.899, df=36, p=0.0126; OD12 SNI- Oxy-Veh vs SNI-Oxy-RBC1HI t=2.277, df=36, p=0.0568) (FIG.18H). RBC1HI also alleviated oxycodone-induced thermal hyperalgesia by Day 12 of active administration (r.m. two-way ANOVA interaction F3,34=11.81, p<0.0001; Tukey’s m.c. Sham-Oxy-Veh vs Sham-Oxy-RBC1HI q=9.016, df=68, p<0.0001) (FIG.18I). No thermal hypersensitivity was observed in female mice during active oxycodone administration (FIG.18J). Example 7 HDAC1/2 inhibition reversed emotional behavioral abnormalities associated with spontaneous oxycodone withdrawal. [0216] The impact of HDAC1/2 inhibition on emotional behaviors after spontaneous oxycodone withdrawal in both SNI and Sham male mice was investigated. Mice received RBC1HI (e.g., Compound A) once daily for 5 weeks (e.g., QD for 5 weeks), starting immediately with oxycodone exposure. Various behaviors at time points matching experiments from FIG.2 were assessed. The treatment paradigm is depicted in FIG.8A- prov and FIG.19A. After 12 or 14 d of withdrawal, anxiety-like behaviors were assessed using the marble burying assay SNI alone, oxycodone withdrawal alone and a combination of oxycodone withdrawal with SNI produced heightened anxiety-like behaviors as assessed by the number of marbles buried in 30 min. Sham-Oxy and SNI- Oxy groups displayed marble burying behavior similar to that of Sham-Sal animals after pre-treatment with RBC1HI (e.g., Compound A), demonstrating significantly reduced marble burying in oxycodone withdrawal groups, independent of peripheral nerve injury. As expected, SNI groups of mice trended towards increased marble burying as compared to Sham-Sal (FIG.8B, FIG.19B). (SNI two-way ANOVA interaction F_1,27=21.1, p<0.0001; Sidak’s m.c. SNI-Oxy-RBC1HI vs SNI-Oxy-Veh t=8.324, df=27, p<0.0001) (Sham two-way ANOVA interaction F1,30=1.303, p=0.2627; Sidak’s m.c. Sham-Oxy- RBC1HI vs Sham-Oxy-Veh t=3.119, df=30, p=0.008). [0217] Consistent with the findings in male mice, HDAC1/2 inhibition sham-Oxy female mice also displayed reduced marble burying behavior during the withdrawal phase after RBC1HI pre-treatment (unpaired t-test t=3.663, df=11, p=0.0037) (FIG.11A, FIG.19A, FIG.19B). Compound A pretreatment reversed stress-related behaviors as shown by total immobility time in the forced swim test (FST) (FIG.8C). No significant effects were observed in the FST between pain-naïve mice undergoing oxycodone withdrawal. Pre- treatment with Compound A (.e.g., RBC1HI) resulted in a significant reduction of immobility time in male SNI-Oxy mice (two-way ANOVA drug treatment F1,52=4.787, p=0.0332; Sidak’s m.c. SNI-Oxy-Veh vs SNI-Oxy-RBC1HI t=2.627, df=52, p=0.0444). [0218] The impact of Compound A (e.g., RBC1HI) treatment on deficits in sociability and social novelty recognition was assessed. Inhibitionin male groups of mice. RBC1HI did not affect spatial exploration during the habituation phase of the paradigm (FIG.19D). RBC1HI treatment reversed the deficit in sociability observed in the SNI-Oxy group (FIG.19E) (SNI two-way ANOVA interaction F_1,26=3.209, p=0.0849; Sidak’s m.c. SNI- Oxy-RBC1HI Social Target vs No Target t=3.88, df=26, p=0.0013). Interestingly, RBC1HI not only reversed a lack of social novelty recognition induced by peripheral neuropathy under a withdrawal state, but it actually increased the time SNI-Oxy-RBC1HI animals spent with the novel mouse (FIG.19F) (SNI two-way ANOVA interaction F1,26=9.833, p=0.0042; Sidak’s m.c. SNI-Oxy-RBC1HI Familiar vs Stranger, t=4.331, df=26, p=0.0004). This treatment did not have any measurable effect on Sham-Sal groups (FIGs.8E-G) of mice, but significantly reduced marble burying in Sham-Oxy female mice (FIG.24). Overall, these findings suggest that RBC1HI treatment efficiently alleviates sensory and affective signs of oxycodone withdrawal under chronic pain states. [0219] By establishing a novel paradigm of prolonged oxycodone exposure, the inventors effectively captured sensory, emotional, and motivational abnormalities that characterize chronic opioid exposure and spontaneous withdrawal under neuropathic pain and pain- free states. The inventors show that chronic oxycodone administration and withdrawal under neuropathic pain states promote maladaptive sensory and affective symptoms that are more severe than those observed in Sham mice receiving the same oxycodone regimen. Bioinformatic analyses revealed unique transcriptional signatures in reward- related brain regions (NAc, mPFC, and VTA) in response to long-term neuropathic pain and oxycodone withdrawal. Despite differences in gene expression adaptations, several common biological pathways and upstream regulators associated with oxycodone withdrawal in both SNI and Sham mice were identified. This study also demonstrated that inhibition of HDAC1/2 prevented behavioral deficits observed with oxycodone withdrawal especially under states of prolonged neuropathic pain. No tolerance is observed to the antiallodynic and antihyperalgesic effects of RBC1HI, as mice respond to the drug following several weeks of treatments (FIG.18). [0220] Within the disclosed paradigm, the inventors captured the breadth of side effects associated with spontaneous withdrawal from prolonged exposure to opioids^{39, 40, 41}. Previous studies in humans have also demonstrated adverse outcomes in neuropathic patients treated with chronic oxycodone^{6, 42, 43, 44}. In line with these studies, the inventors found exacerbated behavioral deficits with opioid dependence under long-term neuropathic pain states. Using established behavioral paradigms of sensory hypersensitivity, the inventors showed that chronic oxycodone exposure produces opioid- induced hyperalgesia that persists up to seven days after discontinuation of drug treatment in both SNI and Sham groups. Notably, the inventors demonstrated that chronic oxycodone treatment in SNI groups produced thermal hyperalgesia which was observed as soon as at Day 5 of treatment. Recent studies have documented that heroin and oxycodone withdrawal in rodents is manifested by deficits in emotional and social behaviors^{39, 45}. While each of these studies uses different treatment regimens and age groups, they both demonstrate the robust effects of opioid withdrawal on mouse behavior. The work described herein, describes the emergence of emotional deficits at earlier timepoints in SNI mice. The present disclosure teaches that Sham-Oxy, SNI-Sal, and SNI-Oxy groups displayed increased latency to eat in a novel arena, reflecting deficits in anxiety/motivational states. Similar observations were made with other assays measuring motivational or anxiety states with several deficits being selectively manifested in SNI- Oxy groups. For example, at early time points of oxycodone withdrawal deficits in sociability were observed during withdrawal only in long-term SNI cohorts. The combination of oxycodone withdrawal and SNI promoted anxiety-like behavior in the light-dark test but not in the marble burying assay. However, the reduction in marble burying observed in SNI-Oxy cohorts may also reflect a loss of motivation (i.e., indifference) to react to environmental stressors. Notably, oxycodone withdrawal had different outcomes in the running wheel assay, depending on the pain state. SNI or oxycodone treatment in pain-free states trended towards an increase in running activity, whereas SNI-Oxy decreased running, perhaps reflecting once again a motivational state. Future studies applying operant tasks and conditioned place aversion protocols will further test this hypothesis. The oxycodone regimen used in males promotes sensory deficits over the 3-week withdrawal period in females as well, although several behaviors, such as oxycodone-induced hyperalgesia (16 hrs after injection) were only observed in male mice. Without being bound by theory, it is believed that a different drug dose or timing of behavioral assessment may be required to observe hyperalgesia in female mice. Notably, data was not collected on sociability upon oxycodone withdrawal, since the behavioral protocols employed did not work well with female mice, who showed a strong bias towards one side during habituation. Furthermore, different drug regimens and assay time points may be required for studies with female mice, and current lab efforts are directed towards the development of paradigms for studies on female cohorts. Given the robust sex differences reported for pain and addiction mechanisms^{45, 46, 47}, future studies will also involve modifications of the existing paradigms for more extensive understanding of transcriptomic mechanisms in female cohorts of mice. The current working example, utilized bulk tissue sequencing analysis, which was sufficient to depict gene expression signatures among various treatments, but this methodology does not provide insight into cell-type specific differential gene expression. Future work with single nucleus sequencing methodology is expected to complement these findings and to highlight neuronal and microglial subpopulations of interest. [0221] While the molecular mechanisms underlying the actions of heroin and morphine in brain circuits mediating physical dependence and addiction have been investigated^{39, 48, 49,} 50, the mechanisms underlying oxycodone actions and the impact of chronic pain states on opioid responses are poorly understood. The differences were identified in transcriptional signatures in the NAc and mPFC of oxycodone withdrawal between chronic neuropathic and pain free states Moreover an inverse relationship was found in the effects of oxycodone withdrawal between long-term SNI and Sham groups in the VTA. This differential pattern of expression reflects the diverse response of brain regions mediating sensory and affective signs of oxycodone withdrawal between neuropathic and pain-free groups (FIG.17). Previous studies have highlighted key differences in oxycodone- induced gene expression in adult vs adolescent mice and the long-lasting effects of oxycodone on dopamine receptor expression across the NAc and VTA^{51, 52}. [0222] Similar transcriptional programs following oxycodone withdrawal and chronic neuropathic pain were observed in the NAc and mPFC, (-log10(p-value)>1.3). In Sham groups, distinct enriched oxycodone withdrawal transcriptional programs were observed across all brain regions surveyed. While in several cases, commonly enriched transcriptional programs were identified, such as cell adhesion in the NAc and mPFC, all three brain regions display robust, unique transcriptional signatures. For oxycodone withdrawal in Sham groups, the NAc was enriched for biological pathways involved in axon guidance, nervous system development, and chemical synaptic transmission, the mPFC for collagen fibril organization and DNA methylation cysteine, and the VTA for multicellular organism development, neuron differentiation, and neuropeptide signaling pathway. The transcriptional programs enriched for oxycodone withdrawal with chronic pain included chemical synaptic transmission, signal transduction (NAc), potassium ion transport, regulation of membrane potential (mPFC), and cellular response to tumor necrosis factor and cellular response to interferon-gamma (VTA). [0223] Several human studies highlight maladaptive increases in activity within brain reward pathway components in chronic pain patients^{2, 12, 16}. Furthermore, preclinical work shows an influential role of the NAc and VTA in altered motivational and emotional states under chronic pain^{13, 21, 53}. The NAc is directly connected to several brain structures implicated in nociception, including the prefrontal cortex⁵⁴ and amygdalar nuclei^{2, 24}. Evidence from recent preclinical studies indicates that chronic pain states primarily affect the function of the indirect dopamine pathway, which is primarily expressing D2 dopamine receptors⁵⁵. More recent studies have documented the importance of amygdala-NAc projections as well as mPFC-NAc projections in modulating chronic pain states²⁴. Earlier work applied the SNI model and whole tissue RNA-Seq methodology to monitor gene expression adaptations in the murine mPFC, NAc, and periaqueductal gray at two months after the induction of nerve injury. These studies revealed that prolonged SNI states promote sensory and affective-like behaviors and trigger differential expression of several genes and intracellular pathways implicated in mood disorders and nociceptive processing²¹. Notably, several of these canonical pathways are also identified in the datasets from this work to be regulated by long-term SNI, such as G-protein coupled receptor signalling, c- AMP-mediated signalling, and pregnenolone biosynthesis. The current findings also show that oxycodone exposure and withdrawal trigger gene signature patterns in the NAc and mPFC that are similar to those observed under SNI states. As expected, several genes associated with sensory hypersensitivity, pain perception, and pain modulation appear as DEGs in these two studies. These genes include Bdnf, Capn11, and Tph2, amongst others. Likewise, opposite gene regulation was found between SNI and Sham groups of mice with oxycodone withdrawal in genes known to be implicated in depression, anxiety, and pain-like conditions. [0224] Based on bioinformatic predictions, the histone modifier HDAC1, an epigenetic regulator with known actions in addiction⁵⁶ and nociceptive processing^{57, 58, 59}, plays a significant role in modulating gene expression associated with oxycodone withdrawal. The observation that systemic inhibition of Class 1 HDACs effectively prevents sensory hyperalgesia and ameliorates emotional manifestations of oxycodone withdrawal may guide drug discovery efforts towards the development of compounds that can help chronic pain patients who use prescription opioids transition to safer non-opioid medications. Studies causally link HDAC inhibitors to “epigenetic priming”, ⁶⁰ suggesting that the drugs act in brain regions that are primed by a previous stressor such as chronic pain. Without be bound by theory, it is believed that Class 1 HDAC inhibitors might be as efficacious for managing withdrawal from other opioid analgesics (e.g., morphine and fentanyl), a subject that warrants future investigation. [0225] Future work will also investigate the impact of Class 1 HDAC, or more selective HDAC1 inhibitors on the reinforcing actions of opioids and determine their potential for the treatment of addiction disorders. Since HDAC1 inhibitors⁵⁷ and Class 1 HDAC inhibitors attenuate mechanical hypersensitivity, it will be important to delineate the peripheral and central mechanisms by which they ameliorate sensory and affective signs of chronic pain. Without being bound by theory, it is belived that these inhibitors act at several sites within the nociceptive pathways, as well as at several regions that mediate the actions of opioids. [0226] A major concern in pain therapeutics involves managing pain in patients dependent on or addicted to opioid analgesics, and necessitates the development of novel treatment approaches that can be safely used in opioid-exposed patients. Indeed, several clinical studies document that pain patients who are dependent on opioids respond poorly to non- opioid analgesics^{61, 62, 63, 64}. Information from this work will help identify novel genes and pathways that can be targeted to prevent the development of physical dependence or opioid withdrawal in patients receiving long-term opioid treatment. Furthermore, inhibition of Class1 HDACs, and downstream pathways may provide a novel way to manage sensory hypersensitivity associated with chronic neuropathic pain conditions in opioid-naïve as well as in opioid-dependent patients. Methods used in Examples 1-7 Animals [0227] C57BL/6J mice (8-9 weeks old) were obtained from Jackson Laboratories and maintained on a 12-h light/dark cycle with ad libitum access to food and water. All experiments were conducted in accordance with the guidelines of the Institutional Animal Care and Use Committee at Mount Sinai and of the Society for Neuroscience. All behavioral testing occurred during the animal’s light cycle. Experimenters were blinded to treatment groups, and order of testing was counterbalanced during behavioral experiments. Different cohorts of animals were used for various behavioral assays and for RNA sequencing studies. Drug preparation [0228] Oxycodone HCl (Sigma Aldrich) was diluted in 0.9% sterile saline. RBC1HI (Regency Pharmaceuticals) was dissolved in 10% DMSO and 90%-5% dextrose in water, which was used as vehicle. Oxycodone was administered subcutaneously QD (once a day) at 30 mg/kg for 2 weeks. RBC1HI was administered i.p. QD at 3 mg/kg. The 3 mg/kg dose was selected as the lowest dose that suppressed SNI and Oxy withdrawal- related behaviors in pilot studies. Spared nerve injury (SNI) surgery [0229] SNI was performed on the left sciatic nerve, as described previously^21, 22, 65. Briefly, using a stereomicroscope, a skin and muscle incision of the left hind limb at mid-thigh level was performed to reach the sciatic nerve. The common peroneal and sural nerves were carefully ligated with 6.0 gauge silk sutures (Johnson & Johnson International) and transected, and 1–2 mm sections of these nerves were removed, while the tibial nerve was left intact. Skin and muscle were then closed with 4.0 gauge silk sutures (Johnson & Johnson International). In Sham-operated mice, the same procedure was followed, but the nerves were left untouched. Oxycodone spontaneous withdrawal protocol [0230] To monitor oxycodone withdrawal in long-term neuropathic pain and pain-free states, a novel oxycodone exposure paradigm was used. Mice received SNI or Sham surgery and 9 weeks later were injected daily for 14 d with 30 mg/kg oxycodone. Following this treatment, mice were allowed to spontaneously withdraw for 21 d. Sensory signs of spontaneous withdrawal were monitored starting the day after the last oxycodone injection. Thermal and mechanical hyperalgesia was monitored during oxycodone injections and at acute time points of drug withdrawal. Locomotor activity, sociability, marble burying, novelty-suppressed feeding (NSF), voluntary running wheel, and light– dark box activity were monitored during spontaneous withdrawal. For HDAC inhibitor studies mice were injected with Sal or RBC1HI (3 mg/kg i.p.) immediately before oxycodone treatment throughout the period of oxycodone administration and up to 21 d post-cessation of opioid treatment. Behaviors assessed after RBC1HI administration included Von Frey and Hargreaves assays, marble burying, locomotor activity, sociability and social interaction. Von Frey assay [0231] For the assessment of mechanical allodynia, Von Frey filaments^{22, 66, 67} with ascending forces was used, expressed in grams (Stoetling). Each filament was applied five times in a row against the ipsilateral hindpaw, with all mice receiving a filament application before returning for the next application to the first mouse. Hindpaw withdrawal or licking was marked as a positive allodynia response. A positive response in three of five repetitive stimuli was defined as the allodynia threshold. Hargreaves test for thermal hyperalgesia [0232] Mice were placed in Plexiglas boxes on top of a glass surface (IITC Life Science), and the latency to withdraw the injured hindpaw (left) was measured after a high-intensity heat beam (40%) was applied to the mid-plantar area (IITC Life Science). Two measurements were obtained with a 10-min interval, and the average was defined as the thermal nociceptive threshold. An intensity level of 40 and cut-off time of 15 sec was used to avoid potential tissue damage⁶⁸. Hindpaw withdrawal or licking was marked as a positive allodynia response. Hot plate assay [0233] A 42°C hot plate was used to assess thermal hypersensitivity to a non-noxious stimulus. Briefly, an animal was placed on a hot plate in a plastic cylindrical enclosure. A cutoff time of 120 seconds was used, and the latency to respond was recorded upon seeing a positive response This was defined as a hindpaw shake/lick or a jump. Marble burying [0234] The marble burying test was conducted under red light conditions as previously described⁶⁹. This assay was performed at the beginning of the second withdrawal week (day 9). After 1 h acclimation to the testing room, mice were placed in a standard hamster cage filled with 15 cm of corn-cob bedding and topped with 20 glass marbles. After 30 min, the mice were removed and the number of marbles fully or partiality buried (60% buried) was counted by two blinded observers and the % of marbles buried was calculated. Marbles that were covered more than 60% were counted as buried. Novelty suppressed feeding (NSF) [0235] A modified NSF was performed after mice were single-housed and food restricted overnight, before testing, to assess stress and motivation-like behavior⁷⁰. On the day of testing, mice were habituated to the testing room for at least 1 h. Under red light conditions, mice were placed into a 40 × 40 × 20 cm arena with wood-chip bedding covering the floor and a single standard chow food pellet in the center of the arena. Mice were placed in the corner of the box, and the latency to eat was scored for up to 8 min. A video-tracking system (Ethovision, Noldus) measured locomotor activity. At the end of the test, mice were transferred to their home cage and the latency to eat in home cage was recorded by a stopwatch with a cutoff of 5 min. Data was analyzed as latency to eat in novel arena and latency to eat in home cage. Total distance traveled was also assessed. ROUT test Q=1% was used to identify outliers within the dataset. Voluntary wheel running [0236] A wireless running wheel activity monitoring system (Low-Profile Wireless Running Wheel for Mouse, Med Associates) was used. Mice were habituated for 2 d in their home cage with the running wheel apparatus⁷¹. On testing days, each mouse was monitored for 1 h. Mice that ran <100 cycles/h were excluded from the study. Activity was calculated as the total number of revolutions during the testing period. Forced swim test (FST) [0237] The FST was conducted following 1 h of habituation to the test room. Mice were placed individually in beakers containing 3 liters of 25 ± 1°C water for 6 min with ambient lighting. Immobility was recorded using a Canon HD Camcorder (VIXIA HF R600). An independent experienced observer recorded total immobility times for 5.5 min, starting 30 s after the beginning of the assay and the latency to immobility (Sci. Signal. 2017, 10). Dark/Light chamber preference [0238] An automated Med Associates place conditioning apparatus⁷² with equal size compartments, has been used for monitoring preference for a bright light vs a dark compartment⁷³. One side of the CPP chamber is illuminated by the overhead light located on the lid of the CPP apparatus. The other side is covered by black lid covers. Identical mesh floors were used for both sides. Mice were placed in the central compartment and allowed to explore the apparatus for 5 min. Data are calculated as % time spent in each compartment and presented as mean±SEM. Sociability and social novelty recognition test [0239] Mice are placed in a two-choice field with an empty grid cage placed in each outer corner of the closed quadrants. For habituation, a subject mouse was allowed to freely explore the U-shaped two-choice field for 8 min. For the sociability and social interaction test, the subject mouse was allowed to explore the field containing a social target on one side and an inanimate grid cage on the other side for 8 min. For the social novelty recognition test, the field contains a social target 1 (an earlier stranger, which was used as the social target in the sociability test) on one side and a social target 2 (a new stranger) on the other side. The subject mouse was allowed to explore the field for 8 min. The mice were videotaped for 8 min and then scored using the Ethovision Tracking System for the following: the total time spent in the quadrant with the social target, the inanimate grid cage and the novel social target²⁶. Mice with strong bias for one side at Habituation (over 65% on one side) were excluded from the experiment. RNA extraction and RNA-Seq library preparation [0240] 21 d after oxycodone treatment cessation, brains were removed rapidly, placed into ice-cold PBS, and sliced into 1 mm-thick coronal sections in a slice matrix. Bilateral punches were made from VTA (16 gauge), NAc (14 gauge), and mPFC (12 gauge) and flash-frozen in tubes on dry ice (n = 4–6 per group)²¹. Total RNA was isolated with TriZol reagent (Invitrogen). All RNA samples were determined to have A260/280 values ≥ 1.8 (Nanodrop); samples for RNA-Seq had RIN values > 9 (BioAnalyzer, Agilent).500 ng of purified RNA was used to prepare libraries for sequencing using the Truseq mRNA library prep kit (Illumina RS-122-2001/2). NAc, mPFC, and VTA samples were pooled (2 animals/sample) prior to library preparation, and were sequenced on an Illumina Hi-seq 2000 apparatus with 125-nt single-end reads at Beckman Coulter Genomics (currently Genewiz). Samples were multiplexed to produce >30M reads/sample. qPCR [0241] RNA was extracted as above from NAc, mPFC, and VTA tissue punches from independent cohorts of SNI-Oxy, Sham-Oxy, SNI-Sal, and Sham-Sal male mice (n = 8-13 animals per group) and converted to cDNA using SuperScript III (Invitrogen 18-080- 400). Primer efficiency and specificity were verified; sequences are given in Table 1. Real-time semi-quantitative qPCR was performed using SybrGreen Fast master mix and standard cycling conditions on a Quant Studio 7 and analyzed by the 2−∆∆Ct method with Gapdh as a control gene. Genes were semi-randomly chosen across levels of significance and brain regions, and only protein-coding genes with high-quality primer validation were included. [0242] Table 1. Primer sequence used for qRT-PCR validations

Bioinformatic analysis [0243] Read alignment, read counting, and differential analysis were performed using HISAT2⁷⁴ HT-Seq ⁷⁵, and the DESeq2 R package, respectively ⁷⁶. Differential analysis aimed to dissect oxycodone withdrawal vs Sal treatment effects in SNI and Sham was performed using a 2 × 2 factorial design with the following formula: log(exp) ∼ SNI + Oxycodone + SNI: Oxycodone. The differential lists were defined by a p-value cutoff of <0.05 and log2 (fold change) of <−0.5 or >0.5. Only terms with p-value <0.05 were reported. Venn diagrams and heat maps were generated using BioVenn-web application (http://www.biovenn.nl/) and Morpheus (https://software.broadinstitute.org/morpheus) software respectively. Pathway analysis was conducted using ingenuity pathway analysis (IPA). For pathway analysis, a cutoff p-value of <0.003 was applied to the output pathways^{21, 72}. Rank-rank hypergeometric overlap (RRHO) RNA-Seq analysis [0244] Full threshold-free differential expression lists were ranked by the −log10(p-value) multiplied by the sign of the fold change from the DESeq2 analysis. RRHO was used to evaluate the overlap of differential expression lists between oxycodone-withdrawing SNI and Sham cohorts. A two-sided version of this analysis was used to test for coincident and opposite enrichment. RRHO difference maps were produced for pairs of RRHO maps (SNI-Oxy vs Sham-Sal control compared to Sham-Oxy vs. Sham-Sal control, and Sham- Oxy vs. Sham–Sal control compared to SNI-Oxy vs. SNI-Sal control). Statistical analysis [0245] Data were analyzed using Graph Pad Prism 9 software and aforementioned R packages. For the experiments monitoring behavioral responses over time, a two-way repeated-measures ANOVAs was used followed by Tukey’s post hoc tests. For two-factor designs, a two-way ANOVA was used followed by Sidak’s post hoc test. For data containing a single independent variable, an unpaired two-tailed t tests was used. Results are expressed as mean±SEM. F and t values for each dataset and analysis are provided in the figure legends..Significance levels are displayed as *p<0.05, **p<0.01, ***p<0.001, ****p<0.0001. Additional Descriptions for Select Figure Legends [0246] FIG. 13. (FIG. 13A) Schematic timeline depicting oxycodone exposure in male chronic SNI and Sham mice. (FIG. 13B). Weight was impacted by oxycodone administration in both SNI and Sham cohorts as compared with Sham-Sal treated controls (Sham, Sal n=11, Oxy, n=16; SNI, Sal n=11, Oxy, n=14). No significant weight change was observed between SNI controls (SNI-Sal) as compared to Sham-Sal. (FIG. 13C). Oxycodone exposure produced significant and progressive thermal hyperalgesia in SNI mice (SNI-Oxy) at 5 d of oxycodone administration as compared to the Sham-Oxy group. Oxycodone-induced thermal hyperalgesia continued during spontaneous withdrawal in SNI-Oxy mice. Sham-Oxy mice displayed oxycodone-induced thermal hyperalgesia only during spontaneous withdrawal at early time points (WD4) (Sham-Sal n=8, Sham-Oxy, n=10; SNI-Sal n=8, SNI-Oxy n=9). (FIG.13D). Oxycodone-induced mechanical allodynia was observed in Sham cohorts at 13 d of drug administration. During spontaneous withdrawal, Sham-Oxy mice displayed mild but significant mechanical allodynia up to 14 d post-drug cessation as compared to Sham-Sal controls. SNI-Oxy mice show significantly decreased mechanical allodynia during oxycodone administration (D13) compared to all earlier time points under nerve injury, but thresholds returned to baseline levels during drug withdrawal (Sham, Sal n=8, Oxy, n=10; SNI, Sal n=8, Oxy n=9). (FIG.13E). In a separate cohort, oxycodone alleviated SNI-induced mechanical allodynia 5 hrs after administration (13 d of daily treatment) (Sham, Sal n=14, Oxy, n=15; SNI, Sal n=14, Oxy n=15). Data indicate mean ± SEM. Significance (p<0.05) was calculated by means of two-way ANOVA with Tukey’s post-hoc test for B-D and Sidak’s post-hoc test for direct comparison of Sham-Oxy vs Sham-Sal (*p<0.05, **p<0.01, ***p<0.001, ****p<0.0001), SNI-Oxy vs Sham-Sal, (^#p<0.05, ^##p<0.01, ^###p<0.001, ^####p<0.0001), SNI-Oxy vs SNI-Sal (^ΦΦΦΦp<0.0001). Abbreviations: Oxy=Oxycodone; Sal=Saline, WD=Withdrawal Day, OD=Oxy administration Day. [0247] FIG. 14. (FIG. 14A). Schematic timeline depicting oxycodone exposure and behavioral assessment in male chronic SNI and Sham mice. (FIG. 14B). 5d post- oxycodone withdrawal anxiety-like behaviors were assessed using the light-dark assay. SNI-Oxy mice spent less time in the light chamber as compared to Sham-Sal controls. Oxycodone withdrawal decreased the time spent in the light chamber in the SNI-Oxy group compared to the Sham-Oxy group (Sham-Sal n=13, Sham-Oxy, n=11; SNI-Sal n=14, SNI- Oxy, n=12). (FIG.14C). In the marble burying assay (Day 9), Sham-Oxy mice and SNI- Sal mice buried significant more marbles as compared with Sham-Sal controls. The effect of oxycodone withdrawal was significant on the number of marbles buried between SNI- Oxy and Sham-Oxy mice. Sham-Oxy mice buried significantly fewer marbles compared to SNI-Oxy mice (Sham-Sal n=13, Oxy, n=12; SNI, Sal n=12, Oxy, n=12). (FIG.14D), (FIG. 14E). Male mice were subjected to a sociability assay 12 d post-oxycodone withdrawal. (FIG. 14D). Mice from all cohorts showed no preference for either of the empty cages during the habituation phase as measured by % time spent with either object. (FIG.14E). During the sociability test, time spent by subject mice in the social target-containing field vs. empty cage-containing side field was enhanced amongst all groups tested (Sham-Sal, Sham-Oxy, SNI-Sal) with the exception of the SNI-Oxy group (Sham-Sal n=16, Sham- Oxy n=13; SNI Sal n=16 SNI Oxy n=16) (FIG 14F). At 15 d of oxycodone withdrawal, male mice were deprived of food for 24 h and then assessed in the NSF paradigm, where latency to eat was monitored in a novel environment vs home cage. The latency to eat in novel environment was significantly affected in Sham-Oxy, SNI-Sal, and SNI-Oxy groups as compared with the Sham-Sal controls. (FIG.14G). The latency to eat in home cage was affected by oxycodone withdrawal in Sham groups only. (FIG.14H). Total distance was significantly affected by oxycodone withdrawal in SNI-Oxy and Sham-Oxy (FIG. 14I). Running wheel performance was assessed at 17 d of oxycodone withdrawal. The effect of oxycodone on voluntary running wheel was significant between Sham-Oxy and SNI-Oxy groups of male mice. (Sham, Sal n=7, Oxy, n=8; SNI, Sal n=9, Oxy, n=9). (FIG. 14J). (Right) At 18 d of oxycodone withdrawal, mice were habituated to the locomotor boxes for 80 min and then received a challenge low dose of oxycodone (1 mg/kg s.c.). SNI-Oxy mice that had been previously exposed to oxycodone demonstrated increased locomotor activity. (FIG. 14L). (Left) Locomotor activity across conditions at 110 minutes (20 min after injection) and at 180 minutes (90 min after injection). Data represent mean ± SEM. For two-way ANOVA multiple comparisons testing between two groups * and ** denotes p<0.05 and p<0.01 respectively. Data represent mean ± SEM. [0248] FIG. 15. (FIG. 15A). Schematic paradigm for tissue collection of brain regions for bulk RNA-Seq studies from adult male C57Bl/6 mice. (FIG. 15B), (FIG. 15E), (FIG. 15H). Venn diagrams representing the number of DEGs altered by chronic pain states (SNI- Sal vs Sham-Sal), oxycodone withdrawal in Sham (Sham-Oxy vs SNI-Sal) and oxycodone withdrawal under chronic nerve injury states (SNI-Oxy vs Sham-Sal). (FIG.15C), (FIG. 15F), (FIG.15I). Representative union heat maps of DEGs in matched comparisons across NAc, mPFC, and VTA respectively; yellow indicates increasing log2FC of gene expression; blue represents decreasing expression. (FIG. 15D), (FIG. 15G), (FIG. 15J). Threshold-free comparison of DEGs by RRHO for NAc, mPFC, and VTA. Each pixel represents the overlap between the transcriptome of each comparison as noted, with the significance of overlap (−log10(p-value) of a hypergeometric test color coded. Lower left quadrant includes co-upregulated genes, upper right quadrant includes co-downregulated genes, and upper left and lower right quadrants include contra-regulated genes. Genes along each axis are sorted from most to least significantly regulated from the middle to outer corners. [0249] FIG.16. Venn diagrams depicting overlap of genes altered by oxycodone withdrawal under in SNI-Oxy vs. SNI-Sal and in Sham-Oxy vs. Sham-Sal in (FIG.16A). NAc, (FIG. 16D) mPFC and (FIG 16G) VTA These graphs also show respective union heat maps of commonly regulated DEGs between SNI-Oxy vs SNI-Sal and Sham-Oxy vs Sham-Sal conditions in the NAc, mPFC, and VTA, as well as associated gene ontology (GO) terms or predicted drug targets. Top predicted upstream regulators of Sham-Oxy vs. Sham-Sal and SNI-Oxy vs. SNI-Sal DEGs in NAc ((FIGs.16A, 16C), mPFC (FIGs.16E, 16F), and VTA (FIGs 16H,16I). Top predicted upstream regulators of SNI-Oxy vs Sham-Sal control DEGs, in NAc, mPFC and VTA. [0250] FIG. 17. (FIGs. 17A, 17B). RRHO threshold-free comparisons of DEGs between NAc, mPFC, and VTA for oxycodone withdrawal with SNI and Sham groups of adult male mice. Each pixel represents the overlap between the transcriptome of each comparison as noted, with the significance of overlap (−log10 (p-value) of a hypergeometric test color coded. The lower left quadrant includes co-upregulated genes, the upper right quadrant includes co-downregulated genes, and the upper left and lower right quadrants include contra-regulated genes. Genes along each axis are sorted from most to least significantly regulated from the middle to outer corners. (FIG.17C). Top canonical pathways commonly regulated between Sham-Oxy vs Sham-Sal, SNI-Oxy vs Sham-Sal, SNI-Oxy vs SNI-Sal comparisons in the mPFC, NAc, and VTA. (FIG. 17D). Representation of significantly downregulated CREB Signaling in Neurons pathway in the NAc SNI-Oxy vs SNI-Sal condition. (FIG.17E). Upstream regulator activity predictions across the aforementioned conditions/regions. between oxycodone withdrawal under SNI and Sham states. (FIG. 17F). The genes predicted to be regulated by HDAC1 (upstream regulator) in the mPFC between SNI-Oxy and Sham-Sal groups [0251] FIG. 18. (FIG.18A) RBC1HI promotes partial recovery from mechanical allodynia in groups of male mice with long-term SNI (Sham-Sal, Veh n=7, RBC1HI n=9; SNI-Sal, Veh n=7, RBC1HI n=10). (FIG.18B). Chronic treatment with 3mg/kg RBC1HI prevents the development of oxycodone-induced hyperalgesia in male SNI groups exposed to chronic oxycodone. During spontaneous oxycodone withdrawal, inhibition HDAC1/2 prevents the induction of thermal hyperalgesia in both SNI and Sham mice (Sham-Sal, Veh n=7, RBC1HI n=9; Sham-Oxy, Veh n=8, RBC1HI n=10; SNI-Sal, Veh n=7, RBC1HI n=10; SNI-Oxy, Veh n=8, RBC1HI n=7). (FIG.18C). RBC1HI alleviates SNI-only and SNI-Oxy withdrawal-induced mechanical hypersensitivity on withdrawal Day 7 (SNI-Sal- Veh n=10, SNI-Sal-RBC1HI n=10, SNI-Oxy-Veh n=10, SNI-Oxy-RBC1HI n=10). (FIG. 18D). Graph shows Von Frey thresholds for female mice from the same group at 5 hrs after Oxy administration on Day 10. RCHBH1 alleviates mechanical hypersensitivity in Sal- treated mice but it does not affect the antiallodynic response to Oxy, as Veh and RCB1H1 groups show similar Von Frey responses. (FIG. 18E, 18F). In Sham mice, RCB1H1 prevents the analgesic effects of Oxy on mechanical thresholds and prevents the development of withdrawal-induced mechanical allodynia (Sham-Sal-Veh n=9, Sham-Sal- RBC1HI n=10, Sham-Oxy-Veh n=9, Sham-Oxy-RBC1HI n=10). (FIG. 18G). RBC1HI pretreatment in this group of female mice also prevents the induction of thermal hyperalgesia after SNI with or without withdrawal in the Hargreaves assay. (FIG. 18H). When female Veh and RBC1HI SNI groups are tested in a 42°C hot plate during active Oxy administration, RBC1HI ameliorates thermal hypersensitivity seen in SNI-Oxy mice. (FIG. 18I). RBC1HI effectively alleviates withdrawal-induced thermal hyperalgesia in Sham-Oxy animals. (FIG.18J). No differences were seen between Sham conditions in the 42°C hot plate assay during active Oxy administration. Data indicate mean ± SEM. Significance (p<0.05) was calculated by means of two-way ANOVA with Bonferroni’s post-hoc test. *p<0.05, *** p<0.001 and ****p<0.0001. Veh=vehicle. FIG.19. (FIG.19A) Schematic timeline of experimental design. (FIG.19B) Treatment with RBC1HI decreased anxiety-like behaviors in the marble burying assay two weeks after oxycodone withdrawal in both SNI and Sham groups of male and Sham-Oxy female mice (Sham-Sal, Veh n=7, RBC1HI n=9; Sham-Oxy, Veh n=8, RBC1HI n=10; SNI-Sal, Veh n=7, RBC1HI n=9; SNI-Oxy, Veh n=8, RBC1HI n=7).. (FIG.19C) RBC1HI treatment reduced immobility time in SNI-Oxy mice. (Sham-Sal, Veh n=7, RBC1HI n=7; Sham-Oxy, Veh n=7, RBC1HI n=10; SNI-Sal, Veh n=7, RBC1HI n=9; SNI-Oxy, Veh n=7, RBC1HI n=6) (FIG.19D). 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Kim, D., Paggi, J.M., Park, C., Bennett, C. & Salzberg, S.L. Graph-based genome alignment and genotyping with HISAT2 and HISAT-genotype. Nat Biotechnol 37, 907-915 (2019). 75. Anders, S., Pyl, P.T. & Huber, W. HTSeq--a Python framework to work with high- throughput sequencing data. Bioinformatics 31, 166-169 (2015). 76. Love, M.I., Huber, W. & Anders, S. Moderated estimation of fold change and dispersion for RNA-seq data with DESeq2. Genome Biol 15, 550 (2014). [0252] The disclosed subject matter is not to be limited in scope by the specific embodiments and examples described herein. Indeed, various modifications of the disclosure in addition to those described will become apparent to those skilled in the art from the foregoing description and accompanying figures. Such modifications are intended to fall within the scope of the appended claims. [0253] All references (e.g., publications or patents or patent applications) cited herein are incorporated herein by reference in their entirety and for all purposes to the same extent as if each individual reference (e.g., publication or patent or patent application) was specifically and individually indicated to be incorporated by reference in its entirety for all purposes. Other embodiments are within the following claims. EQUIVALENTS AND SCOPE [0254] In the claims articles such as "a," "an," and "the" may mean one or more than one unless indicated to the contrary or otherwise evident from the context. Claims or descriptions that include "or" between one or more members of a group are considered satisfied if one, more than one, or all of the group members are present in, employed in, or otherwise relevant to a given product or process unless indicated to the contrary or otherwise evident from the context. The disclosure includes embodiments in which exactly one member of the group is present in, employed in, or otherwise relevant to a given product or process. The disclosure includes embodiments in which more than one, or all of the group members are present in, employed in, or otherwise relevant to a given product or process. [0255] Furthermore, the disclosure encompasses all variations, combinations, and permutations in which one or more limitations, elements, clauses, and descriptive terms from one or more of the listed claims is introduced into another claim. For example, any claim that is dependent on another claim can be modified to include one or more limitations found in any other claim that is dependent on the same base claim. Where elements are presented as lists, e.g., in Markush group format, each subgroup of the elements is also disclosed, and any element(s) can be removed from the group. It should it be understood that, in general, where the disclosure, or embodiments of the disclosure, is/are referred to as comprising particular elements and/or features, certain embodiments of the disclosure or embodiments of the disclosure consist, or consist essentially of, such elements and/or features. For purposes of simplicity, those embodiments have not been specifically set forth in haec verba herein. It is also noted that the terms "comprising" and "containing" are intended to be open and permits the inclusion of additional elements or steps. Where ranges are given, endpoints are included. Furthermore, unless otherwise indicated or otherwise evident from the context and understanding of one of ordinary skill in the art, values that are expressed as ranges can assume any specific value or sub-range within the stated ranges in different embodiments of the disclosure, to the tenth of the unit of the lower limit of the range, unless the context clearly dictates otherwise. [0256] This application refers to various issued patents, published patent applications, journal articles, and other publications, all of which are incorporated herein by reference. If there is a conflict between any of the incorporated references and the present disclosure, the specification shall control. In addition, any particular embodiment of the present disclosure that falls within the prior art may be explicitly excluded from any one or more of the claims. Because such embodiments are deemed to be known to one of ordinary skill in the art, they may be excluded even if the exclusion is not set forth explicitly herein. Any particular embodiment of the disclosure can be excluded from any claim, for any reason, whether or not related to the existence of prior art. [0257] Those skilled in the art will recognize or be able to ascertain using no more than routine experimentation many equivalents to the specific embodiments described herein. The scope of the present embodiments described herein is not intended to be limited to the above Description, but rather is as set forth in the appended claims. Those of ordinary skill in the art will appreciate that various changes and modifications to this description may be made without departing from the spirit or scope of the present disclosure, as defined in the following claims. What is claimed is:

Claims

CLAIMS 1. A method of treating a substance use disorder in a subject in need thereof, comprising administering to the subject a therapeutically effective amount of a histone deacetylase 1/2 (HDAC1/2) inhibitor.

2. The method of claim 1, wherein the HDAC1/2 inhibitor is a compound of Formula I:

I, or a pharmaceutically acceptable salt thereof, wherein R¹ is aryl or heteroaryl; R² is H, C₁-C₆-alkyl, or C₁-C₆-alkyl-N(R^a)2; R³ is H, C₁-C₆-alkyl, C₁-C₆-alkyl-N(R^a)₂, or C(O)R^b; or R² and R³, together with the N atom to which they are attached, optionally form a 5 or 6 membered heterocycloalkyl ring, wherein the heterocycloalkyl ring optionally contains a -N(R^c)- moiety and wherein the heterocycloalkyl ring optionally contains a -C(O)- moiety; each R^a is independently H or C₁-C₆-alkyl; R^b is C₁-C₆-alkyl, C₁-C₆-alkyl-N(R^d)2, or a 5 or 6 membered heterocycloalkyl, wherein the heterocycloalkyl is optionally substituted by C₁-C₆-alkyl; R^c is H or C₁-C₆-alkyl; and each R^d is independently H or C₁-C₆-alkyl.

3. The method of claim 2, wherein R¹ is phenyl, thiophenyl, or pyridinyl.

4. The method of claim 2 or 3, wherein R¹ is phenyl.

5. The method of any one of claims 2-4, wherein R² is H or C₁-C₆-alkyl; R³ is C₁-C₆-alkyl-N(R^a)₂ or C(O)R^b; or R² and R³, together with the N atom to which they are attached, optionally form a 5 or 6 membered heterocycloalkyl ring, wherein the heterocycloalkyl ring optionally contains a - C(O)- moiety and wherein the heterocycloalkyl ring optionally contains a -N(R^c)- moiety.

6. The method of any one of claims 2-5, wherein R² and R³, together with the N atom to which they are attached, form piperadine, piperazine, or piperidinone.

7. The method of any one of claims 1-6, wherein the HDAC1/2 inhibitor is a compound of Formula II:

II, or a pharmaceutically acceptable salt thereof, wherein R¹ is aryl or heteroaryl; and R^c is H or C₁-C₆-alkyl.

8. The method of any one of claims 2-7, wherein R^c is H.

9. The method of any one of claims 1-8, wherein the HDAC1/2 inhibitor is Compound

Compound A; or a pharmaceutically acceptable salt thereof.

10. The method of any one of claims 1-9, wherein the subject is addicted to one or more substances selected from the group consisting of alcohol, an opioid, an opiate, and cocaine.

11. The method of any one of claims 1-10, wherein the subject is addicted to alcohol.

12. The method of any one of claims 1-10, wherein the subject is addicted to an opioid.

13. The method of any one of claims 1-10, wherein the subject is addicted to an opiate.

14. The method of any one of claims 1-10, wherein the subject is addicted to cocaine.

15. The method of claim 10, wherein the opioid is selected from the group consisting of oxycodone, hydrocodone, morphine, oxymorphone, fentanyl, codeine, and tramadol.

16. The method of claim 10, wherein the opioid is oxycodone, morphine, or fentanyl.

17. The method of claim 10, wherein the opioid is oxycodone.

18. The method of claim 1, wherein the method comprises reducing one or more symptoms of a substance use disorder or withdrawal.

19. The method of claim 18, wherein the substance use disorder or withdrawal symptom is selected from the group consisting of mechanical hypersensitivity, hyperalgesia, peripheral nerve damage, anxiety, depression, avolition, and photophobia.

20. The method of claim 19, wherein the mechanical hypersensitivity is mechanical allodynia.

21. The method of claim 19, wherein the substance use disorder or withdrawal symptom is hyperalgesia.

22. The method of claim 21, wherein the hyperalgesia is thermal hyperalgesia.