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

Sponsor
Akyso Therapeutics, LLC
Study ID
NCT07064564
Phase
PHASE1
Status
Not Yet Recruiting

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Conditions

  • Opioid Use Disorder

Eligibility Criteria

Sex
ALL
Age
18 Years - 65 Years
Healthy Volunteers
Accepted

Interventions

  • Naltrexone implant, 14.4 grams — DRUG
    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.
  • Naltrexone implant, 9.6 grams — DRUG
    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.
  • Extended-release naltrexone injection, 380 mg — DRUG
    Intramuscular injection of 380 mg extended-release naltrexone (Vivitrol), administered every 4 weeks for 12 months as the active comparator.

Study Details

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.

Key Dates

First listed
Jul 14, 2025
Start date
Apr 1, 2026
Status verified
Feb 2026
Primary completion
Jun 1, 2027
Completion
Mar 31, 2029

Study Design

Enrollment
33 participants (estimated)
Allocation
RANDOMIZED
Intervention model
PARALLEL
Primary purpose
TREATMENT

Arms

  • Experimental: iSTEP-N High Dose Implant
    Participants in this arm will receive a single subcutaneous implant of iSTEP-N at a high dose level (14.4 grams of naltrexone) on Day 1. Participants will undergo pharmacokinetic and safety evaluations for 12 months. Participants with a detectable implant or measurable naltrexone levels at the end of this period may continue in a longer-term follow-up phase. Intervention: Drug: iSTEP-N Naltrexone Implant - High Dose Single 14.4 g subcutaneous implant administered on Day 1.
  • Experimental: Low-Dose iSTEP-N Implant
    Arm Description (Revised - Low-Dose iSTEP-N) Participants in this arm will receive a single subcutaneous implant of iSTEP-N containing 9.6 grams of naltrexone on Day 1. Participants will undergo pharmacokinetic and safety evaluations for 12 months. Participants with a detectable implant or measurable naltrexone levels at the end of this period may continue in a longer-term follow-up phase. Intervention: Drug: iSTEP-N Naltrexone Implant (Low Dose) Single 9.6 g subcutaneous implant administered on Day 1.
  • Active Comparator: Vivitrol Injection
    Participants in this arm will receive 380 mg of extended-release naltrexone (Vivitrol) by intramuscular injection every 4 weeks for 12 months. Blood samples will be collected to evaluate pharmacokinetics and safety. Intervention: Drug: Vivitrol (Extended-Release Naltrexone Injection) 380 mg IM injection every 4 weeks for 52 weeks.

Primary Outcome Measure

Average plasma naltrexone concentration on the last day of each 4-week interval through Week 52 [ Time Frame: Day 28, 56, 84, 112, 140, 168, 196, 224, 252, 280, 308, and 336 ]

Central Contacts

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