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Treatment of Merkel Cell Carcinoma with Navtemadlin and Immunotherapy

A Phase 1b/2, Open-Label Study Evaluating the Safety and Efficacy of KRT-232 in Patients With p53 Wild-Type (p53WT) Merkel Cell Carcinoma (MCC) Who Have Failed Anti-PD-1 or Anti-PD-L1 Immunotherapy, or in Combination With Avelumab in MCC Patients Who Are Anti-PD-1 or Anti-PD-L1 Treatment Naïve

PHASE1; PHASE2 · Kartos Therapeutics, Inc. · NCT03787602

This study is testing a new drug called KRT-232, alone or with another treatment, to see if it helps people with Merkel Cell Carcinoma who haven't had success with other therapies or are new to treatment.

Quick facts

PhasePHASE1; PHASE2
Study typeInterventional
Enrollment115 (estimated)
Ages18 Years and up
SexAll
SponsorKartos Therapeutics, Inc. (industry)
Drugs / interventionschemotherapy, avelumab, immunotherapy
Locations51 sites (Aurora, Colorado and 50 other locations)
Trial IDNCT03787602 on ClinicalTrials.gov

What this trial studies

This clinical trial evaluates the efficacy of KRT-232, a novel oral small molecule inhibitor of MDM2, in treating patients with Merkel Cell Carcinoma (MCC) who have either failed prior anti-PD-1 or anti-PD-L1 therapies or are treatment naïve. The study includes multiple cohorts based on previous treatment history, allowing for a tailored approach to therapy. Patients will receive KRT-232 alone or in combination with the immunotherapy avelumab, with the goal of assessing the safety and effectiveness of this new treatment strategy.

Who should consider this trial

Good fit: Ideal candidates include patients with histologically confirmed Merkel Cell Carcinoma who have either failed prior immunotherapy or are treatment naïve, and meet specific eligibility criteria.

Not a fit: Patients with autoimmune diseases, those requiring systemic immunosuppression, or those with active infections such as HBV or HCV may not benefit from this study.

Why it matters

Potential benefit: If successful, this treatment could provide a new therapeutic option for patients with advanced Merkel Cell Carcinoma who have limited treatment alternatives.

How similar studies have performed: While the use of MDM2 inhibitors is a novel approach in Merkel Cell Carcinoma, similar studies targeting other malignancies have shown promising results.

Eligibility criteria

Show full inclusion / exclusion criteria 
Inclusion Criteria:

* For Cohort 1, 3 and 4 patients must have failed treatment with at least one PD-1 inhibitor or PD-L1 inhibitor for metastatic MCC
* For Cohort 2, patients must not have received any anti-PD-1 or anti-PD-L1 therapy
* For Cohort 3, patients must not have received any prior chemotherapy
* For Cohort 4, patients must have received at least one prior line of chemotherapy
* ECOG performance status of 0 to 1
* Histologically confirmed MCC. Disease must be measurable, with at least 1 measurable lesion by RECIST 1.1
* MCC expressing p53WT based on any CLIA or test approved by local health authority or a validated test (Cohort 1 and 2)
* MCC expressing p53WT based Central Lab test (Cohort 3 and 4)
* Adequate hematological, hepatic, and renal functions

Exclusion Criteria:

* For Cohort 2, subjects must not have autoimmune disease, medical conditions requiring systemic immunosuppression, prior stem cell transplant, or active infection with HBV or HCV.
* Patients previously treated with MDM2 antagonist therapies or p53-directed therapies
* History of major organ transplant
* Patients with known central nervous system (CNS) metastases that are previously untreated
* Grade 2 or higher QTc prolongation (\>480 milli-seconds per NCI-CTCAE criteria, version 5.0)

Where this trial is running

Aurora, Colorado and 50 other locations

+1 more sites — see ClinicalTrials.gov for the full list.

Study contacts

How to participate

  1. Review the eligibility criteria above with your treating physician.
  2. Visit the official trial page on ClinicalTrials.gov for the most current contact information and recruitment status.
  3. Contact the listed study coordinator or principal investigator to request pre-screening. Pre-screening is free and never obligates you to enroll.

View on ClinicalTrials.gov →

Conditions: Merkel Cell Carcinoma, navtemadlin

Last reviewed 2026-05-15 by the Find a Trial editorial team. Information on this page is for educational purposes and is not medical advice. Always consult qualified healthcare professionals about clinical trial participation.