Sidewinder Therapeutics has secured $137m in a Series B financing round to progress its pipeline of bispecific antibody-drug conjugates (ADCs) – marking the continued growth in investor interest over the modality.
Novartis Venture Fund and Frazier Life Sciences co-led this funding round, while life sciences investment giants like OrbiMed, Goldman Sachs and Astellas Venture Management also contributed – allowing Sidewinder to push forward the development of its three-strong bispecific ADC pipeline to the clinic. The company will advance two of these programmes internally, while exploring out-licensing opportunities for the others under its jurisdiction.
Go deeper with GlobalData
Discover B2B Marketing That Performs
Combine business intelligence and editorial excellence to reach engaged professionals across 36 leading media platforms.
According to Sidewinder, its ADC pipeline differs from other drugs within the modality as it targets two receptor co-complexes, potentially creating a more tumour-specific approach to treatment over first-generation ADCs.
The company’s lead asset, SWT012, has already demonstrated the potential to achieve benefit in a preclinical bladder cancer model, as per a company presentation shared with Pharmaceutical Technology. In the study, the bispecific ADC significantly improved cell internalisation and efficacy over the corresponding bivalent, monospecific antibodies. Sidewinder plans to file an investigational new drug application (IND) for SWT012 at the end of 2026.
Alongside its development efforts for SWT012, the San Diego-based biotech is looking to take its lung and colorectal cancer assets, SWT019 and SWT020, to the clinic. Both drugs have shown promise in preclinical studies, and Sidewinder hopes to submit an IND for SWT019 and a DC nomination for SWT020 in the first half of 2027.
Founded in 2023, Sidewinder is focused on developing next-generation ADCs for cancers with larger patient populations that have been typically difficult to treat. This includes solid tumours like head and neck, squamous cell lung and gastrointestinal cancers.
Bispecific ADCs turn heads
Sidewinder’s Series B comes as investors and pharma companies alike take greater interest in bispecific ADCs, which GlobalData analysts tout as a potential game changer for enhanced ADC selectivity and diminished off-target toxicity.
Commercial success for blockbuster modality pioneers like AstraZeneca and Daiichi Sankyo’s Enhertu (trastuzumab deruxtecan) continues to grow, with GlobalData forecasting that the drug’s total sales will reach $5.3bn in 2032.
In October 2025, Takeda became one of several big pharma companies to ink a high-value deal around bispecific ADCs, signing a $11.4bn mega-deal with Innovent Biologics to secure the rights to several drugs – including bispecific ADC IBI3001 – outside of China.
According to GlobalData, parent company of Pharmaceutical Technology, around 84% of bispecific ADCs were in the preclinical or discovery stages in August 2025, though there are four candidates currently in Phase III. This includes Systimmune and Bristol Myers Squibb’s (BMS) izalontamab brengitecan (iza-bren), which recently met its dual primary endpoints in a Chinese Phase III study in triple-negative breast cancer (TNBC).
While bispecific ADCs are more generally in the early stages of development, 52% of all Chinese licensing deals involving ADCs centred around drugs with two targets in 2024 – highlighting the strong interest in this next-generation format.
