Topotecan has been the default second-line option for relapsed small-cell lung cancer since its FDA approval in 1996, and its survival benefit has always been modest. The phase III TAISHAN-302 trial puts a hard number on what “modest” means by comparison: patients receiving the anti-B7-H3 antibody-drug conjugate tambotatug pelitecan (Tam-Peli, YL201) lived a median of 13.3 months versus 9.4 months for topotecan, a 54% reduction in the risk of death (HR 0.46; p less than 0.0001) across 451 randomized patients.
The progression-free survival gap is even wider. Tam-Peli produced a median of 7.4 months without progression compared with 2.8 months on topotecan, a 71% reduction in the risk of progression or death (HR 0.29; p less than 0.0001). The objective response rate tells the same story from a different angle: 59.1% of patients on Tam-Peli responded versus 9.7% on topotecan. Presented at the IASLC 2026 World Conference on Lung Cancer, the findings held across prespecified subgroups including patients with brain metastases, liver metastases, and a chemotherapy-free interval under 90 days, the populations where second-line therapy most often fails.
The safety data carry real weight here. Grade 3 or higher treatment-related adverse events occurred in 46.4% of Tam-Peli patients versus 74.7% on topotecan, and no treatment-related deaths occurred in the Tam-Peli arm. Interstitial lung disease or pneumonitis appeared in 4.9% of patients on Tam-Peli, higher than the 1.4% rate on topotecan, though grade 3 events were low (0.9% in each group) and no grade 4 or 5 events were reported. That ILD signal, small as it is, will draw scrutiny in any regulatory review given its class-wide relevance to ADCs. B7-H3 is broadly expressed across SCLC tumors, with moderate to high expression documented in roughly 64% of cases in prior research, which shapes how far the eligible population could extend if Tam-Peli reaches approval.
The second-line SCLC field has grown more competitive with tarlatamab now in the mix, but the TAISHAN-302 overall survival magnitude is the number that will define Tam-Peli’s path forward. Watch whether the sponsoring team files for regulatory review in China first or pursues parallel submissions, given that the trial was conducted at Chinese centers under the leadership of Li Zhang at Sun Yat-sen University Cancer Center.
Jon Napitupulu is Director of Media Relations at The Clinical Trial Vanguard. Jon, a computer data scientist, focuses on the latest clinical trial industry news and trends.
