Stipple Bio closes USD 100m Series A financing for ADC pipeline

Cambridge, Massachusetts-based Stipple Bio, Inc., a private biotechnology company developing epitope-targeted cancer therapies, has closed a USD 100 million Series A financing round, emerging from stealth as it prepares to advance its lead antibody-drug conjugate candidate toward the clinic.

The round was co-led by RA Capital, a16z Bio+Health, and Nextech Invest, with participation from existing investors Emerson Collective Investments (managed by Yosemite), GV (Google Ventures), LoLa Capital Partners, and GordonMD Global Investments. The company said proceeds, expected to fund operations into 2029, will support advancement of lead candidate STP-100 into multiple early-stage clinical studies and continued expansion of its pipeline through its proprietary Pointillist Platform. Derek DiRocco, PhD, of RA Capital, and Thilo Schroeder, PhD, will join the board of directors alongside existing members including Vineeta Agarwala, MD, PhD, Owen Hughes, Jeff Landau, Aaron Ring, MD, PhD, and Greg Verdine, PhD.

Stipple Bio was founded in 2022 by Aaron Ring, Associate Professor in the Translational Science and Therapeutics Division at Fred Hutch Cancer Center, and Aashish Manglik, Associate Professor of Pharmaceutical Chemistry at UCSF. The company's scientific premise centers on a distinction its founders draw between protein-level and epitope-level tumor targeting. Conventional oncology drug discovery identifies proteins that are overexpressed on cancer cells relative to healthy tissue, but many such proteins retain some expression in normal organs, generating on-target toxicity that constrains dosing. Ring and Manglik built Stipple Bio around the observation that tumor cells can present discrete binding sites — epitopes — on their surface that are physically inaccessible or absent on the same protein as expressed in healthy tissue, due to differences in protein folding, glycosylation, proteolytic processing, and membrane orientation driven by the tumor microenvironment.

The Pointillist Platform operationalizes this concept as a modality-agnostic discovery engine, screening for binders against intact living tumor cells while applying counter-selection against normal tissue counterparts. Identified epitopes can then be formatted into ADCs, T-cell engagers, radiopharmaceuticals, or other therapeutic modalities. The company has described at least two programs at varying stages of maturity, with STP-100 the most advanced.

STP-100 is an ADC incorporating tumor-specific binders selected to avoid on-target/off-tumor toxicity. The company has not publicly disclosed the specific target antigen or indication. It is expected to enter clinical studies in early 2027, with the Series A financing supporting its progression into multiple early-stage trials. A second program remains at the lead series stage, with target and modality not yet disclosed. The company has also indicated that additional epitopes identified through the platform are available for potential collaboration.

Jeff Landau serves as CEO. The company's initial seed financing was provided by a16z Bio+Health, Emerson Collective Investments, and OMX.

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