Antibody drug conjugates bring a targeted approach to the treatment of many types of cancer, but there’s still room for improving this class of therapies. This week, two startups revealed how they aim to advance the targeting abilities of such drugs.
In an antibody drug conjugate, or ADC, a toxic drug payload reaches its cancer destination by leveraging the targeting ability of an antibody designed to bind to a target specific to the tumor. Sidewinder Therapeutics now has $137 million for its ADCs, which employ antibodies designed to go after two targets versus a single target addressed by monoclonal antibodies used in first-generation ADCs.
Bispecific antibodies are already established in cancer treatment. Binding to two targets gives these therapies better specificity to cancer cells, reducing the risk of hitting healthy cells and causing side effects. Sidewinder is leveraging that property to develop bispecific ADCs in which the antibody component of the therapy binds to co-complexes, two targets that are highly expressed on the surface of certain solid tumors. These internally discovered antibodies bind to one receptor that drives cancer and another an internalizing receptor that brings the therapy into the cell. This approach enhances improves the delivery of drug to cancer cells while avoiding healthy cells, the company said.
The specific targets that Sidewinder is pursuing remain confidential for now. But the startup said it’s developing drugs for cancers with limited treatment options and affect large patient populations, such as squamous cell carcinomas in the lung, head and neck cancers, and gastrointestinal cancers. Sidewinder expects its lead program will begin human testing in 2027.
San Diego-based Sidewinder was founded in 2023 with OrbiMed. Sidewinder’s Series B round was co-led by Frazier Life Sciences and Novartis Venture Fund. With the new financing, the startup said it has raised $162 million total to date.
Meanwhile, Stipple Bio is also tinkering with antibodies to achieve better targeting. Using its proprietary technology platform, the startup identifies tumor-specific cell surface epitopes. The company then designs antibodies that can bind to these targets found only on the tumor in order to avoid causing toxicity that happens when a drug also hits healthy cells. Stipple has raised $100 million to advance lead drug candidate STP-100 to a Phase 1 study expected to begin in early 2027.
Cambridge, Massachusetts-based Stipple was founded in 2022 by Dr. Aaron Ring, associate professor, translational science and therapeutics division, at the Fred Hutchinson Cancer Center, and Dr. Aashish Manglik, associate professor of pharmaceutical chemistry at the University of California, San Francisco. The startup’s seed financing came from a16z Bio+Health, Emerson Collective Investments (managed by Yosemite), and OMX. RA Capital Management, a16z Bio+Health, and Nextech Invest co-led Stipple’s latest financing, a Series A round.
“We are building upon deep cancer biology expertise to map, target and unlock tumor-specific epitopes which enable us to develop a pipeline of next-generation precision oncology therapeutics,” Stipple CEO Jeff Landau said in a prepared statement. “This funding positions us to progress STP-100 into the clinic and continue building a broad oncology pipeline.”
Here’s a recap of other recent biopharmaceutical industry financings:
—ReAlta Life Sciences raised $40 million to complete Phase 2 testing of pegtarazimod, which is being evaluated as a treatment for hypoxic ischemic encephalopathy, a brain injury caused by lack of oxygen to the brain during or around the time of birth. ReAlta’s peptide drug is designed to inhibit dysregulated activity of neutrophils and the complement system that drive inflammation. The company did not identify its investors, but said the new financing brings its total raised to date to more than $150 million.
—Diseases of aging biotech Life Biosciences closed $80 million in financing to support its pipeline, including ER-100, which is being evaluated in separate Phase 1 studies in open-angle glaucoma and non-arteritic anterior ischemic optic neuropathy. Life Bio did not disclose any investor information for its latest financing, a Series D round.
—Syneron Bio raised $150 million. The Beijing-based startup said it will use the capital to advance its technology for discovering macrocyclic peptides and advancing its pipeline into clinical development, though no indications were disclosed. Syneron said the Series B financing was led by an unnamed international life science fund with co-lead participation from Decheng Capital and CDH VGC.
—Cardiometabolic disease biotech Ambrosia Biosciences raised $100 million to enter the clinic with a GLP-1 pill for obesity. The company develops oral small molecules that target G-protein coupled receptors (GPCR), such as GLP-1, GIP, and amylin. Ambrosia’s Series B round was led by new investors Blue Owl Healthcare Opportunities, Redmile, and Deep Track Capital. Ambrosia will need to catch up to GPCR biotech Structure Therapeutics, which plans to begin Phase 3 testing of its GLP-1-targeting daily pill.
—Gilgamesh Pharma, a startup spun out following AbbVie’s acquisition of Gilgamesh Pharmaceuticals last year, raised $60 million to support its pipeline of neuropsychiatric therapies. Blixeprodil, formerly known as GM-1020, is on track to begin late-stage clinical testing this year in major depressive disorder. The company’s Series A financing was led by Satori Neuro.
—Oryon Cell Therapies emerged from stealth with $21 million for a neuron replacement therapy in development for Parkinson’s disease. In interim Phase 1b/2a results for five patients that were presented at the recent AD/PD 2026 Annual Conference on Alzheimer’s and Parkinson’s and Related Neurological Disorders, Oryon said its autologous cell therapy was well tolerated with no serious adverse events reported to date. Furthermore, results so far show “early and meaningful motor improvement in all participants.” The new financing is the latest tranche of a Series A round whose investors include Neuro.VC and Byers Capital.
—Immutrin secured £67 million (about $87 million) to support clinical development of a drug to treat cardiomyopathy associated with the inherited disease ATTR amyloidosis. The startup’s drug is an antibody designed to deplete deposits of amyloid protein that lead to organ damage. New investor Frazier Life Sciences led Immutrin’s Series A round.
—Amani Therapeutics raised $25 million for a Phase 3-ready drug combination drug for schizophrenia. AM-01 is a fixed-dose combination of the old antipsychotic clozapine and a novel molecule in-licensed from AstraZeneca. The company believes this combination could overcome the severe neutropenia and the accompanying blood-monitoring requirements that limit use of clozapine. Amani is backed by RTW Investments.
—Earendil Labs revealed $787 million for its AI-driven technology platform, which it is using to produce a pipeline of antibody and biologic drugs for unspecified diseases in cancer and immunology that lack effective treatment options. The Wilmington, Delaware-based startup offered few details about the “financing rounds” that make up the nine-figure capital haul, which included participation from disclosed investors Dimension Capital, DST Global, INCE Capital, Luminous Ventures, Miracle Capital, Sanofi, and Biotech Development Fund (created by Hillhouse and Pfizer).
—Crossbow Therapeutics has $77 million for T cell engagers in development for cancer, including CBX-250, which is in Phase 1 testing for relapsed and refractory blood cancers including acute myeloid leukemia, chronic myeloid leukemia, myelodysplastic syndromes, and chronic myelomonocytic leukemia. Preliminary data are expected by the end of this year. Crossbow will also use the capital to begin clinical development of CBX-663 in hematologic and solid tumors. The Taiho Ventures and Arkin Bio Capital co-led Crossbow’s Series B round.
—R1 Therapeutics launched with $77.5 million to support AP306, a drug in-licensed from China-based Alebund Pharmaceuticals that’s on track for Phase 2b testing. The molecule is a potential treatment for chronic kidney disease patients who develop hyperphosphatemia — elevated phosphate levels in the blood. While currently available hyperphosphatemia treatments lower phosphate levels, R1 says its drug works by blocking the active transport of phosphate in the gastrointestinal tract. AP306 was initially discovered and developed by Chugai Pharmaceutical, which licensed it to Alebund. R1’s Series A round was co-led by Abingworth, DaVita Venture Group, and F-Prime, with additional participation from Curie.Bio, SymBiosis, and U.S. Renal Care.
—Unnatural Products raised $45 million for its platform technology and drug pipeline. The startup uses its technology to develop macrocyclic peptide drugs for “undruggable” targets. Unnatural Products’ disclosed R&D partners include Novo Nordisk, Bicycle Therapeutics, and Orbis Medicines.
—Waiv, a company that uses its AI technology to guide cancer drug selection in clinical practice and drug research, has $33 million to continue developing its technology and commercializing its offerings. The startup was the former diagnostics unit of AI biotech Owkin. OTB Ventures and Alpha Intelligence Capital led Waiv’s new financing.
—Vima Therapeutics extended its Series A round by $40 million to finance Phase 2 test in Parkinson’s disease. The startup’s lead drug candidate is a combination therapy that addresses excessive signaling in the brain associated with a wide range of movement disorders. Vima launched last year with $60 million for Phase 1 testing of its drug, VIM0423, in isolated dystonia. Vima now plans separate Phase 2 tests of the pill in dystonia and Parkinson’s.
—A $120 million Series B round that Atavistik Bio announced at the end of 2025 has expanded with an additional $40 million. The startup will use the capital to support clinical testing of ATV-1601, a small molecule in development for treating the rare bleeding disorder hereditary hemorrhagic telangiectasia.
—Prolium Therapeutics launched with $50 million. The startup’s lead program is an in-licensed T cell engager in early clinical development for systemic sclerosis and other severe autoimmune diseases driven by aberrant B cells. Prolium’s Series A financing came from founding investor RTW Investments.
—Slate Medicines emerged with $130 million to start clinical development of SLTE-1009, an in-licensed antibody that targets the central nervous system protein PACAP to treat migraine. The startup’s drug can be administered as a subcutaneous injection, which would be an advantage over an intravenously infused Lundbeck drug that also targets PACAP and is further along in clinical development.
—BreezeBio, formerly known as GenEdit, unveiled its new moniker along with $60 million in new capital as it prepares to enter the clinic with BRZ-101, an immune modulation therapy in development for type 1 diabetes. The therapy is intended to spark a process that induces regulatory T cells to block the autoimmune response driving the disease. As GenEdit, the startup raised a $26 million Series A round in 2021.
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