HLD-0915 Receives FDA Fast Track Designation for mCRPC Treatment

The US FDA has granted fast track designation to HLD-0915, a novel bifunctional small molecule therapy, for the treatment of patients with metastatic castration-resistant prostate cancer (mCRPC).¹ This designation aims to accelerate the development and review of the investigational drug, which is currently being evaluated in a phase 1/2 clinical trial (NCT06800313).

The fast track program is designed to facilitate the development and expedite the review of drugs that treat serious conditions and have the potential to address an unmet medical need. The designation provides the sponsor with more frequent communication with the FDA, including opportunities for rolling review and potential eligibility for accelerated approval and priority review. For a patient population with limited therapeutic options, this could mean a more rapid path to market for HLD-0915.

HLD-0915 is a first-in-class therapy that operates via a unique "hold and kill" mechanism, a concept central to the company's proprietary Regulated Induced Proximity Targeting Chimeras (RIPTAC™) modality. The drug is designed to selectively target prostate cancer cells by creating a ternary complex, holding together the androgen receptor (a tumor-specific intracellular targeting protein) and an essential effector protein. This complex formation is intended to drive neomorphic protein-protein interactions, thereby abrogating a critical function within the cancer cell and inducing an antitumor effect. This mechanism represents a departure from traditional androgen receptor antagonists and is being investigated for its potential to overcome resistance mechanisms that commonly limit the efficacy of existing precision oncology medicines.

In preclinical studies, orally delivered HLD-0915 demonstrated promising results, including tumor shrinkage and a decline in prostate-specific antigen (PSA) levels. These studies also indicated a favorable therapeutic index, even in models of drug resistance.

The ongoing phase 1/2 open-label, multicenter clinical trial is enrolling patients with mCRPC to assess the safety, tolerability, pharmacokinetics (PK), pharmacodynamics (PD), and antitumor activity of HLD-0915 as a monotherapy.² The study's initial phase will focus on dose escalation to determine the maximum tolerated dose (MTD) or recommended dose for expansion, followed by phase 2 expansion cohorts to further evaluate efficacy and safety.

The clinical landscape for mCRPC has seen significant advancements, but the disease remains a formidable challenge, often progressing despite initial therapeutic interventions. The development of therapies like HLD-0915, which utilize a novel mechanism of action to target the disease, is critical for addressing the unmet medical needs of this patient population. The fast track designation underscores the FDA's recognition of the potential for HLD-0915 to offer a meaningful clinical benefit. As the clinical trial progresses, the oncology community will be closely monitoring the data to understand the role this innovative therapy may play in the future treatment paradigm for mCRPC.

REFERENCES:

1. Halda Therapeutics Receives FDA Fast Track Designation for HLD-0915 for the Treatment of Metastatic Castration-Resistant Prostate Cancer. News release. Halda Therapeutics. August 14, 2025. Accessed August 14, 2025. https://tinyurl.com/yxy9768n

2. A Study of HLD-0915 in Patients With Metastatic Castration Resistant Prostate Cancer (mCRPC). ClinicalTrials.gov. Updated April 16, 2025. Accessed August 14, 2025. https://clinicaltrials.gov/study/NCT06800313