Stipple Bio emerged from stealth with a $100 million Series A round to advance STP-100, an antibody-drug conjugate designed to prevent off-target toxicity. The company says STP-100 uses tumor-specific binders engineered to improve selectivity, targeting a key limitation that can shrink the therapeutic window of existing ADCs. Stipple’s CEO Jeff Landau told investors that the innovation is upstream of the ADC payload itself, focusing on epitope selection and binder engineering to help the drug distinguish tumor cells from healthy tissue. The company said it plans to enter clinical studies in early 2027. With runway extended into 2029, Stipple said it has flexibility for follow-on financing as it leverages its Pointillist Platform to identify additional tumor-specific epitopes and build out new programs.