HLX11 meets pertuzumab equivalence criteria in phase III neoadjuvant breast cancer trial

A randomized, double-blind phase III equivalence trial published in Clinical Cancer Research compared the pertuzumab biosimilar HLX11 with European Union–sourced reference pertuzumab in 908 patients with HER2-positive, hormone receptor–negative early-stage or locally advanced breast cancer. Patients received four neoadjuvant cycles of either agent plus trastuzumab and docetaxel, with 454 patients per arm. The primary endpoint was total pathologic complete response (tpCR), assessed by blinded independent central review.

The tpCR rate was 46.3% (95% CI, 41.6%–51.0%) with HLX11 and 45.8% (95% CI, 41.2%–50.5%) with reference pertuzumab. Equivalence criteria were met: the relative risk was 1.01 (90% CI, 0.90–1.14), and the reported response-rate difference was 0.47 percentage points (95% CI, −5.99 to 6.92). The abstract reported no clinically meaningful differences in other efficacy endpoints, safety, pharmacokinetics, or immunogenicity.

In the adjuvant phase, 192 patients from the HLX11 arm continued HLX11, while 200 reference-arm patients were re-randomized equally to HLX11 or reference pertuzumab. Switching produced no notable safety, pharmacokinetic, or immunogenicity differences. These results support similarity in the studied population, but the primary endpoint was pathologic response rather than survival. Only the abstract was available; detailed adverse-event results, equivalence margins, and long-term outcomes could not be assessed.