Background: AMH and its membrane receptor AMHRII induce regression of Müllerian ducts in the male embryo. AMHRII is constitutively expressed in ovarian granulosa tumors (GCT) and re-expressed in ~70% of gynecological tumors. GM102, a low-fucose IgG1 antibody, binds AMHRII and acts through macrophage engagement via CD16 high affinity binding, resulting in enhanced tumor phagocytosis. Methods: In the completed escalation part, AMHRII-positive ovarian, cervical and endometrial cancer patients (pts), with measurable disease, Performance Status ≤1 and adequate organ function, received GM102 1 to 20mg/kg every 2 weeks (q2w) then 7 and 10mg/kg weekly (qw) in 8 successive cohorts. Expansion phase will include granulosa, epithelial ovarian and cervical cancers. The objective was to determine a recommended dose (RP2D) from safety, pharmacokinetics, pharmacodynamics (PD) and GM102 anti-tumor activity (RECIST) and change in tumor growth rate (TGR = % change in tumor volume/month pre-treatment vs. after 2 cycles). PD included circulating immune cells (CIC) (ICOS, CD14, CD16, CD64, CD69) and in paired biopsies, macrophage (CD68, CD163, CD16) and T cell (CD3, CD4, CD8, FoxP3, Granzyme B) markers. Results: 27 pts with AMHRII+ gynecological tumors (including 4 GCTs) received 1 to 21 GM102 infusions. Terminal half-life was 130-200hrs. No dose limiting toxicity was observed. Treatment-emergent toxicities were mostly grade 1-2 (including rash, influenza-like symptom, 1 pt each). One pt had grade 3 anorexia and weight loss. 8/17 (47%) evaluable pts exhibited a decrease in TGR [45%-169%] under GM102. Among 4 GCT pts, 2 had a partial response and inhibin B decreased in 3. In CIC, T cell, monocyte and neutrophil activation was observed, and circulating CD16+ monocytes decreased suggesting possible recruitment to tumor site. In paired biopsies, CD16 expression increased in macrophages as well as Granzyme B suggesting GM102-induced cellular cytotoxicity. Conclusions: GM102 was well tolerated at all doses and schedules. RP2D includes 7mg/kg qw and 15mg/kg q2w. The encouraging PD and anti-tumor activity warrants further development of GM102, especially in the rare subtype of GCT. Clinical trial information: NCT02978755