Sidewinder Therapeutics Raises $137M Series B for Bispecific ADCs
Sidewinder Therapeutics, a San Diego-based developer of next-generation bispecific antibody-drug conjugates (ADCs), has raised $137 million in an oversubscribed Series B funding round co-led by Frazier Life Sciences and Novartis Venture Fund. The company's ADCs target receptor co-complexes highly expressed on solid tumors to improve specificity and internalization. The capital will advance its lead bispecific ADC program toward an IND filing by the end of 2026 and clinical development in 2027.
Bispecific ADCs Draw $300M+ in Recent Rounds
The raise aligns with surging investor interest in bispecific ADCs. NEOK Bio emerged from stealth with a $75M Series A in November 2025 to nominate two bispecific ADC candidates for the clinic. Adcytherix secured €105M ($115M) Series A in October 2025 for novel payload ADCs targeting solid tumors. Adcendo completed an oversubscribed $135M Series B in late 2024. Sidewinder's focus on co-complex targeting positions it to capture share in this competitive rush to clinic.
Solid Tumors Evade Single-Target ADCs
Current ADCs often struggle with solid tumors due to limited specificity, leading to off-target toxicities and narrow therapeutic windows. Sidewinder targets squamous cell carcinomas in lung and head/neck cancers, plus gastrointestinal cancers like colorectal, where effective treatments remain scarce. Traditional single-target approaches fail to fully exploit tumor biology, restricting efficacy in heterogeneous solid tumors.
Receptor Co-Complexes Unlock ADC Precision
Sidewinder engineers bispecific ADCs that bind oncogenic driver receptors alongside internalizing receptors forming co-complexes on tumor cells. This dual engagement enhances payload delivery specificity and internalization compared to monospecific ADCs. The platform uses internally discovered bispecific antibodies paired with Lonza/Synaffix's site-specific linker-payload technology via a multi-target license announced in January 2026.
As Daniel Estes from Frazier Life Sciences noted:
“Sidewinder’s novel bispecific ADC pipeline has the potential to address key hurdles limiting safety and efficacy.”
Preclinical data for lead candidate SWT012 in bladder cancer models supports progression to IND by end-2026.
Blue-Chip Syndicate Signals Validation
The oversubscribed round brings total funding to $162M since founding in 2023, with participation from OrbiMed, Goldman Sachs Alternatives, DCVC Bio, Samsara BioCapital, Longwood Fund, Astellas Venture Management, and Alexandria. Frazier and Novartis Venture Fund's leadership underscores conviction in bispecific ADCs amid ADC inflection point. New board additions include Daniel Estes, Michal Silverberg, Josh Richardson, and John Hamer, bolstering strategic guidance for clinical push.
ADC Market Scales to $32B by 2033
The global ADC market reached $12.26B in 2024 and projects growth to $32.11B by 2033 at 10.49% CAGR. Over 15 ADCs are now marketed, with 200+ in pipelines expanding beyond HER2/TROP2 to solid tumors. Bispecific innovations address toxicity challenges, driving capital into next-gen designs like Sidewinder's.
Another estimate pegs 2026 TAM at $14B, growing at 11% CAGR through 2035.
Serial Founder Fuels Rapid Progress
Co-founder and CEO Eric Murphy brings proven oncology expertise, having co-founded Kinnate Biopharma (acquired by XOMA in 2024) and led Alterome Therapeutics to $232M total funding. Co-founder Ryan Corcoran, Director of MGH's Gastrointestinal Cancer Center, provides precision oncology insight for GI targets. President Robert McRae adds operational depth from public biotechs like Palisade Bio.
Clinic Entry Targets 2027 Milestones
Funds enable lead program SWT012 advancement to clinic in 2027, alongside pipeline expansion via Synaffix partnership. Multiple bispecific ADC programs will leverage the clinically validated ADC platform for improved tolerability in solid tumors. CEO Eric Murphy's visibility at JPM Healthcare and Biocom conferences reinforces momentum toward these goals.