GSK’s risvutatug rezetecan wins FDA orphan designation for SCLC

On December 11, 2025, GlaxoSmithKline announced that the U.S. Food and Drug Administration granted Orphan Drug Designation to risvutatug rezetecan for the treatment of small cell lung cancer. The designation follows earlier recognition in Europe and is based on preliminary clinical evidence from the phase I ARTEMIS 001 trial showing durable responses in patients with extensive stage disease.

Risvutatug rezetecan, also referenced in company materials as GSK'227 and GSK5764227 and formerly listed as HS 20093 in earlier reports, is a B7 H3 targeted antibody drug conjugate. GSK describes the agent as a fully human anti B7 H3 monoclonal antibody covalently linked to a topoisomerase inhibitor payload. GSK acquired exclusive worldwide rights to develop and commercialize the asset from Hansoh Pharma, with the exception of mainland China, Hong Kong, Macau and Taiwan.

The FDA designation is the fifth regulatory recognition GSK has cited for the drug and comes after the European Medicines Agency previously granted orphan status for pulmonary neuroendocrine carcinoma, a category that includes small cell lung cancer. The U.S. orphan status signals regulatory encouragement for further study in a disease that remains aggressive and deadly, with limited treatment options for patients who relapse after front line therapy.

Support for the designation came from early stage results in ARTEMIS 001. Reporting from oncology outlets detailed dose escalation across a broad range from 1.0 mg per kg up to 16.0 mg per kg, and a randomized expansion in which patients with extensive stage disease were assigned in a one to one ratio to receive 8.0 mg per kg or 10.0 mg per kg administered every three weeks. Those early reports described durable responses among patients in the expansion cohorts, data that regulators cited when granting orphan status.

GSK is advancing risvutatug rezetecan across multiple solid tumors including lung, prostate and colorectal cancers, and has a global phase III trial registered for relapsed extensive stage small cell lung cancer under the identifier NCT07099898. Orphan designation does not indicate approval but offers incentives intended to encourage development for rare diseases, a regulatory pathway that can speed clinical work and bolster support for larger trials.

Beyond clinical implications, the designation raises questions of access and equity. Small cell lung cancer disproportionately affects underserved communities where late diagnosis and limited access to specialized care are common. The structure of the commercial rights deal leaves mainland China Hong Kong Macau and Taiwan outside GSK's exclusive territory, a factor that may influence regional availability and pricing strategies if the drug advances to approval.

For patients and families facing small cell lung cancer, the new designation represents cautious hope. It underscores the need for continued enrollment in clinical trials and sustained attention from policymakers to ensure that regulatory incentives translate into equitable access to effective treatments when they become available.