CSPC's Anituximab: Two Phase III Datasets Presented at ESMO 2026
nashnova research
CSPC Pharmaceutical's annitumab presented two Phase III studies at ESMO 2026 — both selected as late-breaking abstracts. Gastric cancer second-line OS showed a 61% reduction in death risk; the breast cancer first-line trial was simultaneously published in the *New England Journal of Medicine*, making the two readouts a pivotal moment for the drug's commercial trajectory.
What is annitumab, and why does it matter?
Annitumab (brand name: Ennituo®) is a bispecific antibody developed by CSPC Pharmaceutical (01093) — it targets two distinct, non-overlapping sites on the HER2 protein, giving it a broader attack surface than traditional single-target antibodies like trastuzumab (Herceptin).
Its mechanism works on three fronts: blocking the HER2 signaling pathway, boosting immune-cell killing of tumor cells (ADCC and CDC effects), and forcing cancer cells to internalize and downregulate their HER2 receptors.
This means → annitumab is designed to suppress HER2-positive tumors from multiple angles simultaneously — the rationale behind pitting it directly against established standard-of-care regimens.
Gastric cancer second-line: what does a 61% drop in death risk look like?
The KC-WISE trial enrolled 246 patients with HER2-positive advanced gastric cancer who had failed prior trastuzumab therapy — 125 randomized to annitumab, 121 to the control arm.
The headline number: median overall survival was 19.6 months for annitumab vs. 9.6 months for the control (HR = 0.39, P < 0.0001) — a 61% reduction in death risk. In plain terms = control-arm patients lived a median of under 10 months; annitumab patients lived roughly 20 — more than doubling survival time.
Progression-free survival — how long before the tumor worsens — was equally striking: 7.1 months vs. 2.7 months (HR = 0.35). This reflects a drug that not only extends life but meaningfully delays disease progression.
How did safety look — good news and caveats?
Good news: zero treatment-related deaths in the annitumab arm, versus 5 in the control arm.
The caveat is hematological toxicity: Grade ≥3 neutropenia — a sharp drop in white blood cells — hit 33.1% of annitumab patients vs. 24.8% in controls; anemia ran 25.8% vs. 14.0%.
This means → annitumab cleared the "not fatal" bar more cleanly, but its blood-related side effects are heavier, demanding closer routine blood monitoring in clinical use. This pattern — stronger efficacy, shifted side-effect profile — is common in oncology.
Breast cancer first-line: why is simultaneous NEJM publication a big deal?
The HEALER trial enrolled 885 patients with HER2-positive advanced breast cancer, comparing annitumab in combination therapy against the current standard first-line THP regimen (trastuzumab + pertuzumab + taxane).
Interim analysis: the annitumab combination significantly improved progression-free survival with a manageable safety profile. The study was presented as a proffered paper at ESMO and simultaneously published as an original article in the ***New England Journal of Medicine* (NEJM)**.
In plain terms = NEJM is the world's most prestigious medical journal; publication there means the data passed the toughest peer review in medicine. This is the first breast-cancer clinical result from mainland China to appear in NEJM — a credibility milestone for CSPC in both academic circles and commercial negotiations.
Where does commercialization stand now?
Ennituo®'s gastric cancer indication was approved by China's NMPA in May 2026 for second-line and beyond treatment of HER2-positive advanced gastric cancer. CSPC is the sole marketing authorization holder (MAH) for the approved indication in mainland China.
The breast cancer first-line indication is at the Phase III data-disclosure stage — not yet approved — but the simultaneous NEJM publication gives regulators high-quality evidence to work with.
This means → the gastric cancer indication is already generating revenue; the breast cancer indication is the next commercial milestone. Whether both indications can ramp up successfully will be the market's key test of CSPC's pipeline value.
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