iSTEP-N 101b: Pharmacokinetics and Safety Study of Low- and High-Dose Naltrexone Implants vs Monthly Vivitrol in Healthy Volunteers

Summary

This Phase 1b clinical study is evaluating iSTEP-N, an investigational extended-release implant containing naltrexone, a medication used to block the effects of opioids. The implant is placed under the skin of the thigh and is designed to release medication continuously over many months.

The main purpose of the study is to measure blood levels of naltrexone over time after administration of two different doses of the iSTEP-N implant and to compare those levels with the blood levels achieved by Vivitrol®, an FDA-approved injectable extended-release naltrexone given once every month.

The study will enroll healthy adult volunteers aged 18 to 65 years. Participants will be randomly assigned to one of three groups:

* Low-dose iSTEP-N implant
* High-dose iSTEP-N implant
* Monthly Vivitrol injections

Participants will be followed closely for approximately 12 months to measure medication levels and monitor safety, side effects, and overall health. The study will help determine whether the iSTEP-N implant can maintain naltrexone levels comparable to or higher than those achieved with monthly injections, especially during periods when protection from relapse is most important.

Participants who receive an iSTEP-N implant and still have detectable implant material or measurable medication levels at the end of the first year may continue in a long-term follow-up period lasting up to two additional years. During this period, researchers will monitor how long the implant remains detectable and how long medication continues to be released. If the implant remains after two years, participants may choose to have it surgically removed or simply end study participation.

The study is sponsored by Akyso Therapeutics, LLC, with clinical operations conducted at a dedicated clinical research center and oversight provided by an independent Institutional Review Board. All participants undergo screening examinations to confirm eligibility and are carefully monitored throughout participation.

Results from this study will help determine the appropriate dose of iSTEP-N for future clinical trials and support development of long-acting treatment options for opioid use disorder that may reduce the need for frequent injections.

Conditions

• Opioid Use Disorder

Interventions

DRUG

Naltrexone implant, 14.4 grams

Subcutaneous bioresorbable implant containing 14.4 grams of naltrexone, inserted into the thigh on Day 1 and designed to release drug steadily over 12 months.

DRUG

Naltrexone implant, 9.6 grams

Subcutaneous bioresorbable implant containing 9.6 grams of naltrexone, inserted into the thigh on Day 1 and designed to release drug steadily over 12 months.

DRUG

Extended-release naltrexone injection, 380 mg

Intramuscular injection of 380 mg extended-release naltrexone (Vivitrol), administered every 4 weeks for 12 months as the active comparator.

Sponsors & Collaborators

• National Institute on Drug Abuse (NIDA)

  collaborator NIH

• Cenexel JBR

  collaborator UNKNOWN

• Fast-Track Drugs & Biologics, LLC

  collaborator UNKNOWN

• Aliri Bioanalysis

  collaborator UNKNOWN

• Ardena

  collaborator UNKNOWN

• Element Analytics

  collaborator UNKNOWN

• Akyso Therapeutics, LLC

  lead INDUSTRY

Principal Investigators

• Todd Bertoch · MD

Study Design

Allocation

RANDOMIZED

Purpose

TREATMENT

Masking

NONE

Model

PARALLEL

Eligibility

Min Age

18 Years

Max Age

65 Years

Sex

ALL

Healthy Volunteers

Yes

Timeline & Regulatory

Start

2026-04-01

Primary Completion

2027-06-01

Completion

2029-03-31

FDA Drug

Yes