NEW YORK – Byondis said on Monday that the US Food and Drug Administration has issued a complete response letter requesting additional information on trastuzumab duocarmazine, the investigational antibody-drug conjugate it is developing as a treatment for HER2-positive advanced breast cancer.
The Nijmegen, Netherlands-based firm filed a biologics licensing application with the FDA in July 2022, seeking approval for trastuzumab duocarmazine, or SYD985, as a new option for heavily pretreated, metastatic HER2-positive breast cancer patients. The company submitted data from the Phase III TULIP III trial, in which SYD985 improved patients' progression-free and overall survival versus physician's choice therapy. In the trial, Byondis randomized 436 patients who'd received either at least two HER2-targeting therapies or Novartis' Kadcyla (trastuzumab emtansine).
Based on the FDA's initial acceptance of Byondis' BLA, the agency was slated to issue a decision on the application by May 12, 2023. In the complete response letter, the FDA wrote it was suspending its decision because it needed "additional information that requires time and resources that extend beyond the current evaluation period." Byondis did not detail the information the FDA is requesting.
Meanwhile, the firm's regulatory filings for SYD985 in the EU and UK are moving along. In July 2022, the firm filed an application with the European Medicines Agency in HER2-positive advanced breast cancer. Byondis has a deal with German company Medac, which holds exclusive rights to market the antibody-drug conjugate in the EU and UK should regulators approve the drug.
"We continue to believe that SYD985 can present a meaningful treatment option for patients living with HER2-positive metastatic breast cancer," Byondis CEO Marco Timmers said in a statement. "We appreciate the FDA's guidance and support and will carefully evaluate the complete response letter and consider potential next steps."
In the US, Daiichi Sankyo and AstraZeneca's antibody-drug conjugate Enhertu (trastuzumab deruxtecan) is available for previously treated, metastatic HER2-positive breast cancer patients. Since Byondis filed its BLA, the FDA has also approved Enhertu for HER2-low metastatic breast cancer.