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Intratumoral vidutolimod as monotherapy or in combination with pembrolizumab in patients with programmed cell death 1

Mohammed M Milhem1, Yousef Zakharia1, Diwakar Davar2

  • 1University of Iowa, Iowa City, Iowa, USA.

Cancer
|August 3, 2025
PubMed
Abstract

Insights

Vidutolimod, a Toll-like receptor 9 agonist, shows promise for treating advanced melanoma resistant to PD-1 inhibitors. The PS20-A formulation demonstrated acceptable safety and encouraging clinical activity in combination with pembrolizumab.

Area of Science:

  • Oncology
  • Immunotherapy
  • Melanoma Research

Background:

  • Metastatic melanoma resistant to programmed cell death 1 (PD-1) inhibitors presents a significant unmet medical need.
  • Novel therapeutic strategies are crucial for improving outcomes in this patient population.

Purpose of the Study:

  • To evaluate the safety and clinical activity of vidutolimod, a Toll-like receptor 9 agonist, in patients with advanced melanoma refractory to PD-1 blockade.
  • To compare two formulations of vidutolimod (PS20-A and PS20-B) in terms of safety and efficacy, both as monotherapy and in combination with pembrolizumab.

Main Methods:

  • A two-part, open-label, multicenter, phase 1b clinical trial was conducted in adult patients with metastatic/unresectable anti-PD-1-resistant melanoma.
  • Intratumoral vidutolimod was administered with or without systemic pembrolizumab, with two vidutolimod formulations (PS20-A and PS20-B) assessed.
  • Key endpoints included safety assessments (treatment-emergent adverse events) and investigator-assessed objective response rate (ORR) using RECIST v1.1 criteria.

Main Results:

  • The best objective response rate (ORR) was 23.5% for vidutolimod PS20-A plus pembrolizumab, 11.5% for vidutolimod PS20-B plus pembrolizumab, and 20.0% for vidutolimod monotherapy.
  • Median duration of response ranged from 5.6 to 25.2 months, with the longest duration observed for the vidutolimod PS20-A and pembrolizumab combination.
  • Treatment-emergent adverse events (TEAEs) were common, with any-grade TEAEs occurring in 100% of patients; Grade ≥3 TEAEs occurred in 55.3% (part 1) and 37.5% (part 2) of patients, with no treatment-related deaths.

Conclusions:

  • Vidutolimod PS20-A, administered alone or in combination with pembrolizumab, demonstrated an acceptable safety profile in patients with PD-1 blockade-resistant melanoma.
  • The study suggests promising clinical activity for vidutolimod PS20-A, highlighting its potential as a treatment option for this challenging patient group.
Keywords:
CMP‐001Toll‐like receptor 9 (TLR9) agonistimmunotherapymelanomapembrolizumabphase 1bvidutolimod

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