On July 22nd, a clinical trial registration platform showed that Amgen and BeiGene jointly registered a Phase III study, DeLLphi-315, comparing subcutaneous versus intravenous administration of Tarlatamab in participants with recurrent extensive-stage small cell lung cancer after first-line platinum-based chemotherapy.

This is an open-label, multicenter, randomized study planning to enroll 75 participants domestically and 400 internationally. The primary objective is to demonstrate the non-inferiority of the pharmacokinetic parameters for subcutaneous Tarlatamab compared to intravenous administration. Secondary objectives include characterizing the efficacy, safety, tolerability, quality of life, and immunogenicity of both formulations.

Tarlatamab is a DLL3/CD3 bispecific antibody developed by Amgen. In October 2019, Amgen and BeiGene entered a strategic collaboration, which included co-developing and commercializing Tarlatamab in China. In late August 2025, BeiGene transferred its global royalty rights for Tarlatamab, excluding China, to Royalty Pharma for up to $950 million.

Data shows the intravenous formulation of Tarlatamab was first approved in the United States in May 2024 for treating adult patients with ES-SCLC who failed platinum-based chemotherapy. It gained approval in Japan in December of the same year, followed by approvals in the UK, Canada, and other regions throughout 2025. The drug received its first approval in China in April 2026.

Regarding the development of the subcutaneous formulation, Amgen and BeiGene initiated a Phase Ib study, DeLLphi-308, in September 2024 to evaluate the safety, tolerability, pharmacokinetics, and preliminary anti-tumor activity of subcutaneous Tarlatamab in ES-SCLC subjects. Detailed results from this study have not yet been disclosed. The newly initiated DeLLphi-315 study is the first Phase III clinical trial for the subcutaneous administration of Tarlatamab.

Globally, 11 antibody drugs targeting the CD3 + DLL3 combination have entered clinical stages or beyond. Tarlatamab is the world's first and only approved drug in this class. Two other drugs are following closely, having entered Phase III trials: Obrixtamig from Boehringer Ingelheim/Sino Biopharmaceutical and Alveltamig from Zai Lab/AbbVie.

It is noteworthy that in developing the subcutaneous formulation, Tarlatamab also holds a first-mover advantage, being the first DLL3/CD3 drug to advance a subcutaneous dosing regimen to Phase III. If DeLLphi-315 can demonstrate comparable efficacy and safety between the subcutaneous and intravenous formulations, it will strengthen Tarlatamab's leading position in this therapeutic area.