Aptevo Therapeutics, a biotechnology company focused on developing novel immuno-oncology and hematology therapeutics, and Alligator Bioscience, a biotechnology company developing antibody-based pharmaceuticals for tumor-directed immunotherapy, have entered into an agreement to co-develop a novel immunotherapy bispecific antibody candidate, ALG.APV-527, based on Alligator's first generation bispecific antibody, ATOR-1016. The new bispecific candidate was developed using Aptevo's bispecific technology platform and includes proprietary binding elements generated by Alligator's ALLIGATOR-GOLD antibody library. Initiation of cell line development for the manufacturing of clinical material is expected to begin shortly.

Working under a previously executed material transfer agreement, the companies have engineered and selected ALG.APV-527 as a lead bispecific antibody candidate, featuring a novel mechanism of action targeting 4-1BB, a member of the TNFR superfamily of co-stimulatory receptors found on activated T cells, and an undisclosed tumor antigen widely overexpressed in a number of different types of cancer.

Under the terms of the agreement, the parties will jointly own and share equally in the development costs associated with advancing this candidate through to the end of Phase 2 clinical development. At that time, the parties may opt to out-license the candidate or continue further development separately or in partnership. In addition, the agreement provides an option for the companies to develop a second bispecific antibody candidate based on this novel mechanism of action, which would also be jointly owned and funded by Aptevo and Alligator.

The co-stimulatory receptor 4-1BB is known to play an important role in modulating and augmenting the immune response to cancer by promoting the activation, expansion and enhanced effector function of tumor-specific T cells. It is, therefore, an especially promising target for new immunotherapeutic approaches for cancer treatment. If successfully developed, this new bispecific antibody candidate could have utility in the potential treatment of a broad spectrum of cancers including breast, cervical, non-small-cell-lung, prostate, renal, gastric, colorectal and bladder cancers. While this tumor antigen is widely expressed in multiple types of solid tumors, it shows limited expression on normal tissues, suggesting the potential for tumor-directed immunotherapy with improved efficacy and fewer side effects.

"Our collaboration with Alligator Bioscience has unlocked tremendous synergies, enabling us to capitalize on our companies' respective expertise in therapeutic antibody engineering," said Marvin L. White, president and chief executive officer of Aptevo. "The addition of a 4-1BB bispecific candidate expands and diversifies Aptevo's portfolio while demonstrating the flexibility of our ADAPTIR platform in addressing novel mechanisms of action, in addition to redirected T-cell cytotoxicity. Also, importantly, it allows us to pursue an exciting new therapeutic opportunity with broad potential application in the treatment of non-hematological cancers. If proven successful, this new approach would be a significant advance in cancer immunotherapy. We're extremely pleased to collaborate with Alligator Bioscience in the development of novel tumor-targeting bispecific antibody therapies."

"With five immuno-oncology programs currently in development, each with first- or best-in-class potential, this partnership with Aptevo allows us to further build on the promise of bispecific therapeutics for tumor-directed immunotherapy," said Per Norlén, chief executive officer of Alligator Bioscience. "Our technology platform enables the generation of highly functional antibodies with optimal stability and manufacturing properties, merged into an exceptional bispecific antibody using Aptevo's ADAPTIR platform. We look forward to advancing our collaboration with Aptevo on this promising new therapeutic approach."