Drug-Drug Interaction and Safety of AZD4041 Study (Part 1) and Efficacy, Safety, Pharmacokinetics and Pharmacodynamics of AZD4041 Study in Opioid Use Disorder (Part 2).

The purpose of the study is to assess drug-drug interaction (DDI) and safety of AZD4041 and itraconazole in healthy participants (Part 1), and to assess efficacy, safety, pharmacokinetics (PK) and pharmacodynamics (PD) of AZD404 when administered with buprenorphine/buprenorphine + naloxone in participants with moderate to severe opioid use disorder (OUD)

This study will be conducted in 2 sequential parts.

Part 1 (Phase I) will include healthy participants and will be conducted as two separate parts. Part 1a (DDI cohort) is an open-label, fixed sequence study part which will comprise of:

* A Screening Period from Day -28 to Day -3.
* Three treatment periods:

  * Period 1 (Day -2 to Day 5): Participants will be admitted to the clinical unit on Day -2 and will receive a single oral dose of AZD4041 on Day 1. There will be a 5-day washout period.
  * Period 2 (Day 6 to Day 8): Participants will receive itraconazole for 3 days from Day 6 through Day 8.
  * Period 3 (Day 9 to Day 22): On Day 9, participants will receive single oral dose of AZD4041 co-administered with itraconazole. Itraconazole alone will be administered from Day 10 to Day 21.
* A Follow-up Visit: Participants will return to the clinical unit at least 7 days and no later than 14 days after discharge.

Based on the results from Part 1a, an optional part of the study (Part 1b) may be conducted to assess the safety tolerability and PK of AZD4041 after a single oral dose. Part 1b (Single Dose Cohort) will be a randomized, placebo-controlled, double-blind (participant and investigator blinded) study part conducted in healthy participants. This study part will comprise of the following:

* A Screening Period from Day -28 to Day -3.
* A Treatment Period: Participants will be admitted to the clinical unit on Day -2 and will remain in the unit until Day 4, when they will be discharged after completion of all assessments.
* A Follow-up Visit: Participant will return to the clinical unit at least 12 days and no greater than 16 days after the last AZD4041 PK sample.

The results from Part 1 will determine the AZD4041 dose selection and safety margin to be used in Part 2.

Part 2 (Phase IIa) will be a randomized, placebo-controlled, double-blind study. Participants will be randomized to 1 of 2 treatment arms, AZD4041 or placebo, in a 1:1 ratio. Part 2 will consist of:

* A Screening Period from Day -21 to Day -2.
* A Treatment Period: Participants will be admitted to the clinical unit on Day -1 and will receive either AZD4041 or placebo with hydromorphone (as a replacement opioid) on Days 1, 2 and 3, and buprenorphine/buprenorphine + naloxone (as a standard of care for their opioid withdrawal) on Days 4, 5, 6 and 7. Participants who complete the treatment period will have continued access to Suboxone (buprenorphine + naloxone) during their Follow-up period, which will be supplied to participants at discharge (Day 7).
* A Follow-up Visit: Participant will return to the clinical unit at least 7 days and no greater than 9 days after the last AZD4041 dose.

Eligibility Criteria:
Inclusion Criteria:

• Male participants:

* with female partner(s) of childbearing potential (including breastfeeding partner) must be willing to use a reliable method of contraception throughout the study period for 30 days) after final investigational medicinal product (IMP) administration for Part 1a, and for 5 drug elimination half-lives after final IMP administration for Part 1b and Part 2.
* must not donate sperm starting at screening and throughout the study period and for 30 days) after final IMP administration for Part 1a and for 5 drug elimination half-lives after final IMP administration for Part 1b and Part 2.
* with pregnant partner(s) must agree to remain abstinent or use a condom for the duration of the pregnancy throughout the study period and for 5 drug elimination half-lives after final IMP administration.

Part 1

* Body mass index (BMI) within 18.0 kg/m2 to 30.0 kg/m2, inclusive.
* Body weight of within 50 kg to 100 kg, inclusive.
* Non- or ex-smoker (an ex-smoker is defined as someone who completely stopped using nicotine products for at least 180 days prior to the first drug administration).

Part 2

* BMI within the range of ≥ 18 and ≤ 35 kg/m2 at the screening visit.
* Participant has a diagnosis of moderate to severe OUD according to the Diagnostic and Statistical Manual of Mental Disorders, 5th Edition (DSM-5) using the Mini International Neuropsychiatric Interview (MINI) version 7.02.
* Participant is voluntarily seeking treatment for OUD.
* Participant is not currently receiving Medication for Opioid Use Disorder (MOUD), and has not received MOUD within 60 days prior to screening and is:

  * Willing to initiate buprenorphine therapy;
  * Considered to be a good candidate for buprenorphine treatment based on medical and psychosocial history;
  * Has a positive urine drug screen at the initial screening visit and Day -1 for opioids. These may include morphine and metabolites, diacetylmorphine (heroin), codeine, oxycodone, hydrocodone, hydromorphone, fentanyl and metabolites, propoxyphene or oxymorphone.
* Female participants:

  * must not donate ova starting at screening and throughout the study period and 5 drug elimination half-lives after final IMP administration.
  * must not be planning to become pregnant during the study and at least one of the following conditions apply:

    * Woman of non-childbearing potential (WONCBP) and/or
    * Woman of childbearing potential who agrees to follow the contraceptive guidance from the time of informed consent until at least for 5 drug elimination half-lives after final IMP administration.

Exclusion Criteria:

* Participant has a history of attempted suicide or suicidal behavior within 12 months prior to screening or has any suicidal ideation that meets criteria at a level of 4 or 5 by using the Columbia Suicide Severity Rating Scale (C-SSRS) within 12 months prior to Screening or who is at significant risk to commit suicide, as assessed at Screening and at Day -1.
* Male participants with a history of oligospermia or azoospermia or any other disorder of the reproductive system or who are undergoing treatment or evaluation for infertility.
* Females who are lactating or pregnant according to the pregnancy test at Screening or prior to the first study intervention administration.
* A family history of long QT syndrome.
* Any abnormal or clinically significant findings in laboratory test results at Screening.
* Participant has HIV per screening serology test.
* Any clinically important abnormalities in rhythm, conduction, or morphology of the resting electrocardiogram (ECG) and any clinically important abnormalities in the 12-lead ECG.
* History of significant allergy/ hypersensitivity to AZD4041 or to products related to AZD4041 or other study drugs (including excipients of the formulation), as well as history of severe allergy/hypersensitivity reactions (like angioedema) to any drugs.
* Any vaccination (including with COVID-19 vaccine) less than 14 days prior to first study intervention administration.
* Participants who have a history of exposure to psilocybin and 3,4-methylenedioxymethamphetamine (MDMA) within the last 3 months.

Part 1 Only:

* Past medical history of any clinically significant systemic illness including (but not necessarily limited to) cardiovascular, gastrointestinal, pulmonary, hematologic, neurological, hepatic, endocrinologic, metabolic, genito-urinary, musculoskeletal, immunologic, dermatologic, renal and/or major disease.
* Maintenance therapy with any drug for long-term chronic conditions or significant history of drug dependency or alcohol abuse (\> 21 units/week or \> 3 units/day for men; \> 14 units/week or \> 2 units/day for women; intake of excessive alcohol, acute or chronic).
* History of any significant psychiatric disorder according to the criteria of the Diagnostic and Statistical manual of Mental Disorders, 5th Edition (American Psychiatric Association 2013).
* History of any substance use disorder (as per DSM-5 criteria).
* Any clinically significant, medical/surgical procedure or trauma within the 28 days prior to the first study intervention administration.
* Positive urine test result for drugs of abuse or cotinine (nicotine), at Screening or prior to the first study intervention administration
* Positive screening results to hepatitis B surface antigen (HbsAg), or hepatitis C virus (HCV) tests.
* Use of any prescription drugs, including hormone replacement therapy in the 28 days prior to the first study intervention administration.
* Excessive intake of caffeine-containing drinks or food (e.g., coffee, tea, chocolate) as judged by an Investigator.
* Presence of any tongue piercings or history of any tongue piercings in the last 90 days prior to the first study intervention administration.
* Participants who have medical dietary restrictions.
* Participants with a known hypersensitivity to itraconazole (Part 1a only).

Part 2 Only:

* Participant with clinically significant and uncontrolled cardiovascular, gastrointestinal, pulmonary, hematological, neurological, hepatic, endocrinal, metabolic, musculoskeletal, immunologic, dermatologic, renal and/or any other major disease.
* Participants with a history of severe respiratory insufficiency, obstructive sleep apnea not controlled by a continuous positive airway pressure device or narcolepsy or current clinically significant infections.
* Current diagnosis of chronic pain and who require treatment with opioids.
* Participant has an active malignancy or a history of malignancy (except for treated non-melanoma skin cancer) within 5 years of screening.
* Participant has a history of respiratory depression while on buprenorphine-based or other MOUD.
* Participants with active signs or symptoms of hepatitis and requiring treatment; or known or suspected chronic liver disease, including cirrhosis or significant liver fibrosis.
* Participants with current HCV infection.
* Hepatitis B Virus (HBV) infection: Participants with positive hepatitis B surface antigen (HbsAg) or those with a history of Hepatitis B viral infection.
* Participant has known kidney disease and a glomerular filtration rate (GFR) \< 60 mL/min/m2 at screening.
* Participant has comorbid major psychiatric disorders specifically schizophrenia, bipolar disorder or severe major depressive disorder.
* Moderate to severe substance use disorder on any other psychoactive substances (by DSM 5) other than opioids, caffeine or nicotine (eg, alcohol, sedatives).
* If a participant is currently diagnosed with abuse of or dependence on alcohol, the participant will not be allowed to enrol in the study, unless the alcohol abuse/dependence is in full (complete, not partial), sustained (\> 1 year) remission.
* Participants who need to be on prescription central nervous system (CNS) depressant medications including benzodiazepines, during the trial (other than the study interventions).
* Participant has a positive urine drug screen (UDS) results for barbiturates or benzodiazepines at screening or Day -1.
* Participant has a positive urine test for buprenorphine on Day -1.
* Participants with a known hypersensitivity to buprenorphine, naloxone, other opioids or any components of the formulations used.