QLC5508 ADC Phase 1 Results Positive in ES-SCLC, Qilu to Commercialize in China

QLC5508 (MHB088C), a novel B7-H3-targeted antibody-drug conjugate (ADC) from Minghui Pharmaceutical, has shown encouraging results in treating extensive-stage small cell lung cancer (ES-SCLC). Presented at the 2025 World Conference on Lung Cancer (WCLC), the Phase 1 study highlights QLC5508’s prolonged survival and tolerable safety profile in previously treated ES-SCLC patients.

The multi-center Phase 1 trial enrolled 106 patients across three dosing cohorts: 1.6 mg/kg every two weeks (Q2W, n=30), 2.0 mg/kg Q2W (n=46), and 2.4 mg/kg every three weeks (Q3W, n=30). Median progression-free survival (PFS) ranged from 5.52 to 5.95 months, and median overall survival (OS) ranged from 11.50 to 11.73 months. Treatment-related adverse events (TRAEs) of ≥grade 3 occurred in 34.8% to 50.0% of patients, with neutrophil count decrease (17.0%) and white blood cell count decrease (10.4%) being the most frequent. Two patients in the 2.0 mg/kg Q2W cohort discontinued due to interstitial lung disease, and one death due to cachexia was reported in the 1.6 mg/kg Q2W cohort. No major hematological toxicity was observed, underscoring QLC5508’s manageable safety profile.

In a significant business move, Qilu Pharmaceutical acquired exclusive rights to develop and commercialize QLC5508 in Greater China (mainland China, Hong Kong, Macau, and Taiwan) from Minghui Pharmaceutical for up to 1.345 billion RMB (~$186 million), including a 280 million RMB upfront payment and potential milestone payments. Minghui retains global rights outside Greater China and continues to advance QLC5508’s development.

QLC5508 joins a competitive B7-H3 ADC landscape for SCLC. For comparison, MediLink’s YL201 reported a 61% objective response rate (ORR) and 6.2 months PFS in a Phase 1/2 trial. Merck and Daiichi Sankyo’s ifinatamab deruxtecan achieved a 55% ORR and 5.5 months PFS in the IDeate-Lung01 Phase 2 trial. GSK/Hansoh’s GSK5764227 showed a 61% ORR and 5.9 months PFS in the Artemis-001 Phase 1 trial. QLC5508’s efficacy appears competitive, and its ongoing Phase 3 study in China will further clarify its potential.

With robust clinical data and a strategic partnership, QLC5508 is positioned as a promising contender in the B7-H3 ADC space, potentially offering a new treatment option for ES-SCLC and other solid tumors.

Sources

1. Zhou C, Yu Y, Yu X, et al. Safety and efficacy of QLC5508 in previously treated patients with small cell lung cancer: updated data from a phase 1 study. WCLC 2025 Abstract OA06.02. Available at: https://cattendee.abstractsonline.com/meeting/21151/Session/244
2. WCLC 2025 official news. Qilu Pharmaceutical announces updated clinical data for B7-H3 ADC QLC5508. Available at: https://www.qilu-pharma.com/news/qlc5508-wclc-2025
3. PR Newswire. Minghui Pharmaceutical announces strategic partnership and licensing agreement with Qilu Pharmaceutical to develop B7-H3 ADC in Greater China. Available at: https://www.prnewswire.com/news-releases/minghui-pharmaceutical-announces-strategic-partnership-and-licensing-agreement-with-qilu-pharmaceutical-to-develop-b7-h3-adc-in-greater-china-302450962.html
4. BioWorld. Qilu nabs China rights to Minghui's B7-H3 ADC for up to $186M. Available at: https://www.bioworld.com/articles/720092-qilu-nabs-china-rights-to-minghuis-b7-h3-adc-for-up-to-186m
5. Oncology Pipeline. MediLink's YL201 in SCLC. Available at: https://www.oncologypipeline.com/apexonco/esmo-2024-medilink-impresses-small-cell-lung-cancer
6. Merck. Ifinatamab deruxtecan in SCLC: IDeate-Lung01 Phase 2 trial. Available at: https://www.merck.com/news/ifinatamab-deruxtecan-continues-to-demonstrate-promising-objective-response-rates-in-patients-with-extensive-stage-small-cell-lung-cancer-in-ideate-lung01-phase-2-trial/
7. Oncology Pipeline. GSK/Hansoh's GSK5764227 in SCLC. Available at: https://www.oncologypipeline.com/apexonco/esmo-2024-medilink-impresses-small-cell-lung-cancer
8. Clinical Options. B7-H3 ADCs in SCLC. Available at: https://clinicaloptions.com/activities/oncology/b7-h3-adcs-in-sclc/106732/content
9. OncLive. Emerging ADCs in SCLC: Spotlight on B7-H3 and MHB088C. Available at: https://www.onclive.com/view/emerging-adcs-in-sclc-spotlight-on-b7-h3-and-mhb088c