Sutro Biopharma, Inc., a clinical-stage drug development and manufacturing company focused on the application of precise protein engineering to create next-gen oncology therapeutics, has achieved a clinical supply milestone under its collaboration and license agreement with Merck KGaA, and is entitled to receive a milestone payment.

The candidate, M1231, was discovered using Sutro’s XpressCF and XpressCF+ drug discovery and manufacturing technologies and includes a linker-warhead discovered by Sutro. M1231 is a MUC1-EGFR bispecific antibody drug conjugate (ADC) for the treatment of solid tumors and relies on the strand-exchange engineered domain (SEED) platform from Merck KGaA, Darmstadt, Germany to generate bispecific antibody-like molecules.

The milestone was achieved with the delivery of GMP clinical trial supply to Merck KGaA, for the Phase 1 clinical trial testing of M1231 pursuant to a 2014 license agreement. As part of the agreement, Sutro will manufacture M1231 for early clinical supply and is eligible for further milestones and royalties. Merck KGaA will be responsible for filling and finishing the drug product, in addition to its clinical development and commercialization.

Under the terms of the 2014 license agreement, the companies collaborated to discover and develop ADCs utilizing Sutro’s cell-free protein synthesis and site-specific conjugation platforms, XpressCF and Xpress CF+. Financial details were not disclosed.