<jats:p> 3004 </jats:p><jats:p> Background: HER2 ( ERBB2) amplification and/or overexpression is observed in 2–3% of solid tumors, and is often associated with more aggressive disease. Thus far, HER2-targeted therapies are FDA-approved only for breast, gastric, and gastroesophageal cancers. MyPathway (NCT02091141) is a non-randomized, phase 2a multi-basket study assessing the activity of FDA-approved targeted therapies in non-indicated advanced solid tumors with relevant molecular alterations. We report results from the MyPathway HER2 basket, comprising a large, tissue-agnostic cohort of patients (pts) with HER2-altered tumors treated with P + H. Methods: Pts in this analysis were aged ≥18 years and had HER2-amplified and/or overexpressed tumors. Pts received P (840-mg IV loading dose, then 420-mg every 3 weeks [q3w]) + H (8-mg/kg IV loading dose, then 6-mg/kg q3w). The primary efficacy endpoint was investigator-assessed objective response rate (ORR). Other endpoints included disease control rate (DCR, defined by objective response or stable disease >4 mos) and duration of response (DOR). Subgroup analyses were completed by tumor type and KRAS status. Results: Pts were fully enrolled from April 14, 2014 to June 15, 2020. By January 22, 2021, 260 pts were efficacy-evaluable. Confirmed ORR (cORR) was 23.1% (60/260, including 5 complete responses; 95% confidence interval [CI] 18.1–28.7), DCR was 44.2% (115/260, 95% CI 38.1–50.5), and median DOR was 7.9 mos (95% CI 6.2–9.3). In 199 pts with wild-type KRAS tumors, cORR was 25.6% (51/199, 95% CI 19.7–32.3), DCR was 48.7% (97/199, 95% CI 41.6–55.9), and median DOR was 8.3 mos (95% CI 6.2–10.8). In comparison, in 26 pts with KRAS-mutated tumors, cORR was 3.8% (1/26, responder had colorectal cancer; 95% CI 0.1–19.6), DCR was 3.8% (1/26, 95% CI 0.1–19.6), and DOR was 2.7 mos. KRAS status was unknown in 35/260 pts (cORR 22.9% [8/35, 95% CI 10.4–40.1]; median DOR 6.7 mos [95% CI 2.5–12.7]). Clinical outcomes by tumor type are shown in the Table. Conclusions: P+H was active in a wide variety of KRAS wild-type HER2-amplified/overexpressed tumor types, but had limited activity in KRAS-mutated tumors. Clinical trial information: NCT02091141. [Table: see text] </jats:p>