• Fast Track granted for a next-generation, PARP1-selective inhibitor with CNS activity
• Addresses brain metastases harboring BRCA1/2 and/or HRR alterations—an area of high unmet need
• Enables enhanced interaction with FDA, eligibility for rolling review and expedited regulatory pathways

Duke Street Bio, a clinical-stage biotechnology company focused on precision oncology, today announced that the U.S. Food and Drug Administration (FDA) has granted Fast Track designation to DSB2455, its next-generation, CNS-active selective PARP1 inhibitor, for the treatment of patients with brain metastases originating from primary triple-negative breast cancer (TNBC) tumors harboring BRCA1/2 and/or homologous recombination repair (HRR) alterations.

DSB2455 is a potentially best-in-class agent within the PARP1-selective inhibitor space, offering a differentiated profile that may expand therapeutic possibilities in hard-to-treat indications. The compound is a next-generation, highly PARP1-selective inhibitor with demonstrated brain penetrance and potent anti-tumour activity in preclinical models of homologous recombination-deficient cancers, including brain metastases.

The Fast Track designation is intended to facilitate the development of new therapies for serious conditions where there is significant unmet medical need. It allows for more frequent interactions with the FDA, eligibility for rolling review of an NDA, and potential consideration for Priority Review or Accelerated Approval.

“Receiving Fast Track designation for DSB2455 represents an important milestone in our mission to develop more targeted and effective therapies for patients with limited treatment options,” said Alan Wise, Chief Executive Officer of Duke Street Bio. “Next-generation PARP1-selective inhibitors such as DSB2455 are expected to offer a wider therapeutic window than earlier PARP inhibitors, potentially enabling broader use both as monotherapy and in combination with other anti-cancer agents across a range of tumors.”

“DSB2455’s ability to achieve therapeutically relevant concentrations in the CNS represents a key differentiator,” added Dónal Landers, Chief Medical Officer of Duke Street Bio. “This could offer a new treatment option for patients with secondary HRD brain metastases, where clinical need remains high and current therapeutic choices are limited.”

About Fast Track Designation

The FDA’s Fast Track program is designed to accelerate the development and review of new drugs for serious or life-threatening conditions that demonstrate the potential to address unmet medical needs. Companies granted this designation benefit from more frequent communication with the FDA and eligibility for rolling submissions and other expedited review processes.

About Duke Street Bio

Duke Street Bio is a privately held, clinical-stage biotechnology company headquartered in London, United Kingdom. The company is advancing a pipeline of targeted oncology therapies optimised to achieve best-in-class pharmacology to exploit synthetic lethality and other tumor-specific vulnerabilities. For more information, visit www.dukestbio.com.

Forward-Looking Statements

This press release contains forward-looking statements regarding the potential of DSB2455 and Duke Street Bio’s development strategy. Actual results may differ due to a variety of risks and uncertainties, including clinical development outcomes, regulatory decisions, and market dynamics. Duke Street Bio undertakes no obligation to update these statements.