Biosimilar Trastuzumab Shows ORR Equivalence For HER2-Positive Metastatic Breast Cancer

Preliminary results suggest that a biosimilar formulation plus a taxane may achieve comparable overall response rates to trastuzumab plus a taxane in HER2-positive metastatic breast cancer

medwireNews: Heritage Study results suggest that a biosimilar formulation of trastuzumab achieves a comparable overall response rate (ORR) to trastuzumab for patients with HER2-positive metastatic breast cancer.

“Although further assessment is needed to establish long-term clinical outcomes and safety, the availability of a clinically effective biosimilar treatment option for trastuzumab may lead to broader access to this therapy for patients with breast cancer”, the investigators write in JAMA.

The 24-week ORR was 69.6% for the 230 patients from 95 sites in Russia, Eastern Europe and Asia who were randomly assigned to receive the biosimilar plus taxane chemotherapy compared with 64.0% for the 228 patients who were given trastuzumab plus a taxane.

This gave a nonsignificant ratio of 1.09 and an ORR difference of 5.6 percentage points, both of which were within the therapeutic equivalence boundaries, write Hope Rugo, from the University of California in San Francisco, USA, and co-authors.

And these findings were mirrored in the per-protocol analysis including 438 patients, with an ORR ratio of 1.06, they emphasize.

The team also reports secondary 48-week exploratory findings for the study indicating that the biosimilar and trastuzumab groups had comparable rates of tumour progression (41.3 vs 43.0%) and progression-free survival (44.3 vs 44.7%). Nor did overall survival at 48 weeks significantly differ between the arms, at 89.1% versus 85.1%.

JAMA’s Editor in Chief, Howard Bauchner, and co-authors observe in an accompanying editorial that the original research and development of trastuzumab could save manufacturing costs and provide a “potential solution” to the increasing cost of cancer treatment.

“Whether this study will prove to be truly practice changing remains to be seen”, they caution, however, noting that to expand its use in patients who would otherwise not be able to access treatment, manufacturers “must ensure that the pricing of this biosimilar product is responsible and fair and provides access to this important therapy at an affordable price.”

The authors of a second editorial agree: “Unless the price of the trastuzumab biosimilar is set considerably lower than the 25% to 30% discounts typically seen during the last decade for biosimilars entering European markets, treatment will remain inaccessible for far too many patients.

“It is morally indefensible to foster a clinical trials system that recruits participants from low- and middle-resource countries primarily to benefit market competition in richer countries”, write Deborah Schrag and Harold Burstein, both from Dana-Farber Cancer Institute in Boston, Massachusetts, USA.

“The ethical conduct of biosimilar trials requires ensuring that the communities of trial participants should have realistic access to drugs they have helped to develop.”


Rugo HS, Barve A, Waller CF, et al. Effect of a proposed trastuzumab biosimilar compared with trastuzumab on overall response rate in patients with ERBB2 (HER2)-positive metastatic breast cancer. A randomized clinical trial. JAMA; Advance online publication 1 December 2016. doi:10.1001/jama.2016.18305

Bauchner H, Fontanarosa PB, Golub RM. Scientific evidence and financial obligations to ensure access to biosimilars for cancer treatment. JAMA; Advance online publication 1 December 2016. doi:10.1001/jama.2016.18743

Burstein HJ, Schrag D. Biosimilar therapy for ERBB2 (HER2)-positive breast cancer. Close enough?JAMA; Advance online publication 1 December 2016. doi:10.1001/jama.2016.18979

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