Sidewinder Therapeutics raises USD 137 million Series B for bispecific antibody-drug conjugates

San Diego-based Sidewinder Therapeutics [has closed](https://www.businesswire.com/news/home/20260408583837/en/Sidewinder-Therapeutics-Announces-%24137-Million-Series-B-Financing-to-Advance-Precision-Bispecific-ADCs-into-Clinical-Development-for-Cancer) a USD 137 million Series B financing round to advance its pipeline of bispecific antibody-drug conjugates targeting solid tumors, bringing total funds raised to USD 162 million since the company's founding in 2023. The round was co-led by Frazier Life Sciences and Novartis Venture Fund, with OrbiMed — the sole Series A investor — returning alongside new participants including Life Sciences at Goldman Sachs Alternatives, DCVC Bio, Samsara BioCapital, Longwood Fund, Astellas Venture Management, and Alexandria Venture Investments. Concurrent with the close, four new directors joined the board: Daniel Estes from Frazier Life Sciences, Michal Silverberg from Novartis Venture Fund, Josh Richardson from Life Sciences at Goldman Sachs Alternatives, and John Hamer from DCVC Bio. The company said proceeds will be used to advance its lead program toward clinical development, which it expects to initiate in 2027. Sidewinder's approach centers on bispecific ADCs engineered to bind tumor-specific receptor co-complexes — pairings of an oncogenic driver receptor and an internalizing receptor that are co-expressed at elevated levels on certain solid tumors. The company said this dual-receptor targeting is designed to improve both tumor selectivity and intracellular payload delivery relative to monospecific ADCs, which can lose specificity when individual target receptors are present on normal tissue. The bispecific antibodies are derived from internally discovered sequences, and the company has entered a [multi-target licensing agreement](https://www.prnewswire.com/news-releases/lonzas-synaffix-and-sidewinder-therapeutics-announce-multi-target-license-agreement-to-advance-development-of-nextgeneration-bispecific-adcs-302654334.html) with Lonza to apply Synaffix's site-specific linker-payload technologies — including GlycoConnect, HydraSpace, and toxSYN — across multiple pipeline programs. Site-specific conjugation produces a defined drug-antibody ratio, which the company said supports more consistent pharmacokinetics and a wider therapeutic window compared with earlier-generation ADC conjugation methods. The pipeline targets oncology indications with limited existing options, with the company citing squamous cell carcinomas of the lung and head and neck, as well as gastrointestinal cancers including colorectal cancer, as areas of focus. No candidate names, specific receptor target pairs, or trial identifiers have been disclosed publicly; the lead program remains preclinical with first-in-human entry projected for 2027. Sidewinder was co-founded and is led by Eric Murphy, who holds the title of Co-Founder and CEO. The available record does not identify academic co-founders or a university spinout origin for the company's core bispecific targeting concept, and no university technology-transfer arrangement has been publicly disclosed. The Synaffix conjugation technology, accessed via Lonza, represents the one externally documented platform-level licensing arrangement underpinning the pipeline. The ADC sector has attracted sustained investment in recent years as site-specific conjugation and next-generation antibody engineering have expanded the range of targets and tumor types considered tractable. Bispecific ADC formats, which remain earlier in clinical validation than monospecific ADCs, are drawing attention as a potential route to improved selectivity in solid tumor indications where on-target, off-tumor toxicity has constrained dose and efficacy for existing agents. Sidewinder's USD 137 million raise positions it among the better-capitalized preclinical entrants in this segment, though the field includes several companies at more advanced stages of clinical testing. --- Spot something wrong? [Report an issue with this article](https://newsgen-prod.reframedata.com/feedback/bispecific-antibody-drug-conjugates-sidewinder)