In vivo efficacy of anti-ICOS-MMAE ADCs on ICOS⁺PDXs. (A-C) Fourteen mice were engrafted with 5.10⁵  cells of PDXs from patients with SS and divided into 2 groups (anti-ICOS-MMAE ADC and anti-HER2 ADC control). Both treatments were injected IV at days 55, 58, 62, and 65 at a dose of 3 mg/kg. Mice were then euthanized at day 69, and organs were removed, dissociated, and analyzed by flow cytometry (in the blood [A], bone marrow [B], and spleen [C]). (D) Thirty mice were engrafted with 5.10⁵  cells of PDXs from patients with AITL and divided into 3 groups of 10 mice. Treatment began on day 22, when the earliest blasts were detected in the blood (∼0.2 blasts/μL). Anti-ICOS ADC and saline serum (NaCl 0.9%) were injected IV at days 22, 25, 38, and 43 at a dose of 3 mg/kg. Vincristine was administered intraperitoneally on days 22, 29, and 38 at 0.25 mg/kg. *P = .01-.05; ***P < .001.