A Multiple Dose Opioid Challenge Study

This is a multi-site, randomized, double-blind, repeat-dose Phase 2 study to evaluate the
degree and duration of action of multiple doses of CAM2038 q1w in blocking the effects of a
mu opioid agonist (hydromorphone) in patients with moderate or severe opioid use disorder.
The study will involve 4 phases: Screening, Qualification, Treatment, and Follow-up.

The study will enroll a sufficient number of subjects to ensure that at least 48 subjects
complete the study (24 subjects per group with at least 16 females in total). Replacement
subjects may be added at the discretion of the sponsor with the agreement of the
investigator.

Inclusion Criteria:

1. Subjects with a diagnosis of moderate or severe opioid use disorder (Diagnostic and
Statistical Manual of Mental Disorders - Fifth Edition [DSM-V])

2. Self-reported opioid-use of a minimum of 21 days in the 30 days prior to Screening

3. Positive urine drug screen (UDS) for opioids at Screening or at check-in. If UDS is
not positive, subjects must present with physical signs of withdrawal, as determined
by the Investigator.

4. Female subjects of childbearing potential must be willing to use a reliable method of
contraception during the entire study (Screening Visit to Follow-Up phone call)

5. Female subjects of non-childbearing potential should be surgically sterile (i.e.,
have undergone complete hysterectomy, bilateral oophorectomy, or tubal ligation) or
in a menopausal state (at least 1 year without menses), as confirmed by FSH levels.

6. Male subjects with female partners of childbearing potential must agree to use a
reliable method of contraception from Screening Visit through at least 3 months after
the last dose of study drug. Male subjects must also agree not to donate sperm during
the study through at least 3 months after the last dose of study drug.

Exclusion Criteria:

1. Opioid dependent subjects who are actively seeking treatment for their moderate to
severe opioid use disorder.

2. Subjects with positive urine drug screens for buprenorphine, alcohol, barbiturates,
benzodiazepines or methadone on the day of check in to the CRU or breath alcohol if
urine alcohol not tested.

3. Aspartate aminotransferase levels >3 X the upper limit of normal, alanine
aminotransferase levels >3 X the upper limit of normal, total bilirubin >1.5 X the
upper limit of normal, or creatinine >1.5 X upper limit of normal on the Screening
laboratory assessments and at inpatient check-in, or other clinically significant
laboratory abnormalities, which in the opinion of the Investigator may prevent the
subject from safely participating in the study.

4. Any clinically significant abnormality on the basis of medical history, vital signs,
physical examination, 12-Lead electrocardiogram (QTcF ≥450 msec for males or ≥470
msec for females), and laboratory evaluation (including hematology, clinical
chemistry, urinalysis, and serology) at Screening, in the opinion of the
Investigator.

5. Significant symptoms, medical conditions, or other circumstances which, in the
opinion of the Investigator, would preclude compliance with the protocol, adequate
cooperation in the study or obtaining informed consent, or may prevent the subject
from safely participating in study (including, but not limited to, the risks
described as precautions, warnings, and contraindications in the current version of
the Investigator's Brochure for CAM2038).