UK MHRA Grants CStone Approval for Sugemalimab in Stage III NSCLC, Adding a Second Consolidation Immunotherapy Option
The UK Medicines and Healthcare products Regulatory Agency (MHRA) has approved Cejemly (sugemalimab) as a monotherapy for adult patients with unresectable stage III non-small cell lung cancer (NSCLC) whose disease has not progressed after platinum-based chemoradiotherapy. The sugemalimab MHRA approval, announced by CStone Pharmaceuticals on 22 February 2026, makes sugemalimab only the second PD-(L)1 checkpoint inhibitor approved for this indication in the UK and Europe, joining AstraZeneca's durvalumab (Imfinzi), which has held the field since 2018. The decision also marks the second UK indication for sugemalimab; the MHRA and European Commission had previously approved the drug in combination with platinum-based chemotherapy for first-line treatment of metastatic NSCLC. For CStone, a Suzhou-headquartered biotech listed on the Hong Kong Stock Exchange, the approval extends a commercial footprint that the company said now reaches more than 60 countries and regions.
Approved Indication and Dosing Details
The MHRA approved sugemalimab as monotherapy for adults with unresectable stage III NSCLC who express PD-L1 on at least 1% of tumour cells, carry no sensitising EGFR mutations, and have no ALK or ROS1 genomic aberrations. Eligible patients must not have progressed following platinum-based chemoradiotherapy. Sugemalimab is a fully human, full-length IgG4 anti-PD-L1 monoclonal antibody administered by intravenous infusion. CStone Pharmaceuticals UK and European regulatory filings followed the drug's earlier approvals in China, where the National Medical Products Administration (NMPA) has cleared sugemalimab for five indications spanning NSCLC, extranodal NK/T-cell lymphoma, oesophageal squamous cell carcinoma, and gastric/gastroesophageal junction adenocarcinoma. Full prescribing information specific to the UK label had not been published at the time of the announcement; the company said further regulatory filings for additional indications, including gastric cancer and oesophageal squamous cell carcinoma, are planned.
Clinical Evidence From GEMSTONE-301
The approval is based on results from GEMSTONE-301 (NCT03728556), a multicentre, randomised, double-blind, placebo-controlled Phase III trial that enrolled 381 patients with unresectable stage III NSCLC who had not progressed after concurrent or sequential platinum-based chemoradiotherapy. The primary endpoint was progression-free survival (PFS). CStone reported that sugemalimab demonstrated a statistically significant improvement in PFS over placebo and a clinically meaningful prolongation of overall survival. The company did not disclose specific hazard ratios or median survival figures in the announcement. A trial design paper published in BMC Cancer describes the protocol in detail. One design feature that distinguishes GEMSTONE-301 from the PACIFIC trial, which supported durvalumab's approval, is the inclusion of patients who received sequential chemoradiotherapy rather than only concurrent regimens. Because a substantial fraction of stage III NSCLC patients in routine practice receive sequential therapy — often due to comorbidities or performance status — this broader enrolment criterion could widen the population for whom consolidation immunotherapy data exist.
How Sugemalimab Fits the Stage III NSCLC Landscape
Sugemalimab targets PD-L1, blocking its interaction with PD-1 and B7.1 (CD80) on T cells and thereby relieving a key inhibitory checkpoint that tumours exploit to evade immune destruction. This is the same pathway addressed by durvalumab, though the two antibodies differ in isotype: sugemalimab uses an IgG4 backbone, which in principle reduces Fc-mediated effector functions such as antibody-dependent cellular cytotoxicity, while durvalumab is an engineered IgG1 kappa antibody. Whether this structural distinction translates into a differential safety or efficacy profile in clinical practice remains an open question; no head-to-head trials have been conducted.
CStone developed sugemalimab using the OmniRat transgenic animal platform, which generates fully human antibodies. The drug was first approved in China in 2021 and received European Commission approval for metastatic NSCLC in July 2024. The company has established four commercialisation partnerships spanning Europe, the Middle East and Africa, and Latin America, though it has not publicly named all partners. CStone's chief medical officer, Qingmei Shi, noted that sugemalimab in combination with chemotherapy for stage IV NSCLC has received the highest-level recommendation (I, A) in the European Society for Medical Oncology (ESMO) living guideline for non-oncogene-addicted metastatic NSCLC, and said the company anticipates the stage III indication may be incorporated into that guideline.
The standard of care for unresectable stage III NSCLC has been defined since 2018 by durvalumab consolidation after concurrent chemoradiotherapy, based on the PACIFIC trial. Five-year follow-up data from PACIFIC showed overall survival rates of approximately 42.9% with durvalumab versus 33.4% with placebo. However, several unmet needs persist. Patients who receive sequential rather than concurrent chemoradiotherapy have historically lacked direct Phase III evidence supporting consolidation immunotherapy, since PACIFIC excluded them. Patients with PD-L1-negative tumours or with oncogene-driven disease (EGFR, ALK, ROS1) are also excluded from both the durvalumab and sugemalimab labels, leaving these subgroups without approved consolidation options. Real-world data have additionally flagged challenges in timely initiation of consolidation therapy and management of immune-related pneumonitis following thoracic radiation.