Similarity of CT-P6 and trastuzumab remain with longer follow-up

SAN ANTONIO – After a 2-year follow-up, the efficacy and cardiac toxicity profile between CT-P6, a trastuzumab biosimilar candidate, and trastuzumab as neoadjuvant and then adjuvant therapy for patients with early HER2-positive breast cancer remains consistent with previous results.

Similarity in safety and efficacy at 1 year was previously demonstrated in the phase 3 trial, as well as similarity in cardiac toxicity at a median of 19 months. Updated disease-free survival, overall survival, and cardiac toxicity with a median follow-up of 2 years will be presented by Francisco J. Esteva, MD, PhD, of the Laura & Isaac Perlmutter Cancer Center at NYU Langone Health, New York, in a poster presentation at the San Antonio Breast Cancer Symposium.

For the trial, 549 patients with HER2-positive early breast cancer were randomized to receive CT-P6 (n = 271) or trastuzumab (n = 278) in combination with docetaxel (cycles 1-4) and 5-fluorouracil, epirubicin, and cyclophosphamide (cycles 5-8). CT-P6 or trastuzumab was administered at 8 mg/kg (cycle 1 only) followed by 6 mg/kg every 3 weeks. After surgery, patients received CT-P6 or trastuzumab monotherapy and then entered the follow-up period.

A total of 528 patients entered the follow-up period, with a median duration of 27 months. Disease-free and overall survival were similar in the two arms in both the per-protocol set and the intention-to-treat set. In the intention-to-treat set, the 2-year disease-free survival was 86% (95% confidence interval, 80%-90%) in the CT-P6 arm and 90% (95% CI, 85%-93%) in the trastuzumab arm. Two-year overall survival was 97% (95% CI, 93%-98%) in the CT-P6 arm and 98% (95% CI, 96%-99%) in the trastuzumab arm. Median disease-free and overall survival have not been reached, according to the abstract.

No new cases of heart failure were reported during the follow-up period. Left ventricular ejection fraction was similar in both arms. The efficacy and cardiac toxicity profile between CT-P6 and trastuzumab were consistent with published data.

“CT-P6 was consistently well tolerated with a similar cardiotoxicity profile to that of trastuzumab through a long duration of follow-up,” Dr. Esteva and authors said.

The study sponsor is Celltrion, maker of CT-P6. Dr. Esteva disclosed a consulting or advisory role with Celltrion, as well as relationships with various other pharmaceutical companies.

SOURCE: Esteva FJ et al. SABCS 2018, Abstract P6-17-03.