BeOne Medicines (Nasdaq: ONC; formerly BeiGene) announced that tarlatamab, a DLL3/CD3-targeting bispecific T-cell engager (TCE) co-developed with Amgen, has received conditional approval from China’s National Medical Products Administration (NMPA) priority review. The indication covers adult patients with extensive-stage small cell lung cancer (ES-SCLC) who have progressed after at least two prior systemic therapies, including platinum-based chemotherapy. The decision marks the first approval of a DLL3/CD3 bispecific TCE in China. The molecule, marketed as Imdelltra by Amgen, will be sold under the tradename Antaishi by BeOne Medicine.
The conditional approval was granted under priority review, consistent with the NMPA’s pathway for serious diseases with unmet need. The indication is restricted to adults with ES-SCLC after at least two prior lines of therapy — a narrower prior-treatment requirement than the US label, which covers patients after at least one prior line. A supplemental application based on Phase III DeLLphi-304 data was accepted for review in China in July 2025. The current approval is based on earlier-phase data while that supplemental review continues.
The NMPA decision rests primarily on two studies. The Phase II DeLLphi-301 trial (NCT05060016), a global open-label multicenter study in relapsed or refractory SCLC patients previously treated with platinum chemotherapy and at least one additional line, showed an objective response rate of 40% (95% CI: 31–51) and a median duration of response of 9.7 months (95% CI: 2.7–20.7+). The Phase IIa DeLLphi-307 study, conducted in Chinese patients with ES-SCLC who had received at least two prior lines, produced efficacy results described as consistent with the global study. Across pooled safety data from DeLLphi-300, DeLLphi-301, and DeLLphi-304, common adverse events included cytokine release syndrome (CRS), decreased appetite, pyrexia, dysgeusia, constipation, anemia, fatigue, and nausea. CRS events were predominantly Grade 1 or 2, occurred mainly during the first two doses, and were managed with supportive care.
Tarlatamab was originally developed by Amgen, which originated the molecule through its BiTE platform — itself built on technology acquired from Micromet in 2012. Under a 2019 global strategic collaboration, BeOne and Amgen share responsibility for clinical development, regulatory filing, and commercialization in mainland China. Globally, tarlatamab received accelerated approval from the US FDA in May 2024 based on DeLLphi-301 data and was converted to full approval in November 2025 following results from the Phase III DeLLphi-304 study. The China conditional approval follows that trajectory, extending the drug’s regulatory footprint to a country that reports approximately 160,000 new SCLC cases annually.
The disease context underscores the limited options available to this patient population. Small cell lung cancer accounts for approximately 15% of lung cancer cases globally, with around 70% diagnosed at the extensive stage. Despite initial sensitivity to platinum-based chemotherapy, most patients relapse within six months, and later-line treatment options have historically been sparse. DLL3 is expressed in 85%-96% of SCLC tumor cells with minimal expression in normal tissues, making it a tractable target for tumor-directed T-cell engagement. Tarlatamab binds DLL3 on tumor cells and CD3 on T cells, triggering T-cell activation and tumor cell lysis — a mechanism distinct from checkpoint inhibitors and chemotherapy.
The SCLC treatment landscape has seen several regulatory actions in recent years. In the US, durvalumab (Imfinzi, AstraZeneca) received approval in December 2024 for limited-stage SCLC following the Phase III ADRIATIC trial, while lurbinectedin combined with atezolizumab (Jazz Pharmaceuticals/Genentech) was approved in October 2025 as first-line maintenance therapy for ES-SCLC based on the IMforte trial. Tarlatamab’s China approval adds a later-line T-cell engager option to a landscape that has otherwise been dominated by platinum-based chemotherapy and, more recently, PD-L1 checkpoint inhibition. The drug has been incorporated into guidelines from the National Comprehensive Cancer Network, the American Society of Clinical Oncology, and China’s CACA guidelines.