Phoenix Molecular Designs Dosed First Patient in Dauntless-1, a Phase 2 Clinical Trial of PMD-026 in Combination with Fulvestrant for RSK2-high Breast Cancer

PMD-026 is a first-in-class and best-in-class pan-RSK inhibitor
Favorable mPFS demonstrated in Phase 1/1b as a monotherapy in RSK2-high metastatic breast cancer patients.

Excerpt from the Press Release:

SAN DIEGO and VANCOUVER, British Columbia, Feb. 20, 2025 (GLOBE NEWSWIRE) — Phoenix Molecular Designs (PhoenixMD), a female-founded clinical-stage precision oncology company focused on developing precise cancer therapeutics, today announced the dosing of the first patient in their Phase 2 clinical trial, Dauntless-1. The Dauntless-1 trial will evaluate the therapeutic potential of PMD-026 (a first-in-class oral pan-RSK inhibitor) in combination with fulvestrant, and clinical efficacy in +HR/HER2-/ RSK2-high patients with locally advanced or metastatic breast cancer.

This trial will enroll second-line HR+/HER2-/RSK2-high metastatic breast cancer patients who have been treated previously with a CDK4/6 inhibitor and have developed resistance to it. Among these patients, 70% will express high levels of nuclear RSK2. Fulvestrant, a selective estrogen receptor degrader (SERD), is a commonly prescribed second-line endocrine therapy. However, its therapeutic effect is often limited to ~2-3 months as a single agent, thus creating a need for additional therapeutic options. Notably PMD-026 is highly synergistic with fulvestrant in preclinical models, including those models with an acquired resistance to CDK4/6 inhibitors. PhoenixMD will evaluate its targeted agent, PMD-026, in combination with fulvestrant and is prospectively enrolling RSK2-high patients to receive this combination therapy in its Phase 2 Dauntless-1 trial.

“We are especially excited about our Phase 2 trial because PMD-026 has the potential to overcome CDK4/6 resistance based on pre-clinical and early clinical studies” said Sandi Dunn, PhD, Founder and CEO of Phoenix Molecular Designs. “In our Phase 1/1b monotherapy study, PMD-026 demonstrated favorable tolerability, with no peripheral neuropathy, hair loss, or hyperglycemia. Moreover, PMD-026 demonstrated a median progression free survival (mPFS) of 4.8 months in patients with RSK2-high tumors versus only 1.3 months in patients with RSK2-low tumors in a subset analysis of patients who had no more than five prior therapies. We believe that PMD-026 as a combination therapy represents a promising new approach to treating advanced breast cancer.”

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