Background: T-DXd is an antibody drug conjugate targeting HER2 and is approved in HER2-expressing breast (BC) and gastric (GC) cancers. HER2 expression is prevalent in other solid tumors. The efficacy of current treatments (Tx) in these populations, including studies with HER2-directed Tx, is modest, revealing a significant unmet medical need. Clinically meaningful activity of T-DXd was seen in HER2-expressing tumors in a phase 1 study (NCT02564900). Methods: DP-02 (NCT04482309) is an open-label phase 2 study of T-DXd 5.4 mg/kg q3w in pts with HER2-expressing (immunohistochemistry [IHC] 3+ or IHC 2+ by local or central testing) locally advanced or metastatic disease that progressed after ≥1 systemic Tx or that has no Tx options. Cohorts with biliary tract (BTC), bladder (URO), cervical (CC), endometrial (EC), ovarian (OC), pancreatic (PC), or other tumors (excluding BC, GC, colorectal cancer, and non-small cell lung cancer) were enrolled. Efficacy and safety were analyzed in all pts who received ≥1 dose of T-DXd. The primary endpoint was investigator-assessed confirmed objective response rate (ORR). Secondary endpoints included duration of response (DOR), disease control rate, progression-free and overall survival, and safety. Results: At data cutoff (16 Nov 2022; median follow-up, 9.7 mo), 267 pts had been treated (median, 2 prior lines of Tx [range, 0-13]); 75 pts were IHC 3+ and 125 were IHC 2+ by central testing. In all 267 pts, the ORR was 37.1% and median DOR (mDOR) was 11.8 mo; in pts with IHC 3+ expression, the ORR was 61.3% and mDOR was 22.1 mo. ORR per cohort is shown in all pts and those with centrally confirmed HER2 IHC 3+ or IHC 2+ expression. Grade (G) ≥3 adverse events (AEs) occurred in 58.4% of pts; 11.6% discontinued Tx due to AEs. Adjudicated drug-related interstitial lung disease/pneumonitis occurred in 18 pts (6.7% [G1, n=6; G2, n=11; G5, n=1]). Conclusions: This is the first tumor-agnostic global study of T-DXd in a broad range of HER2-expressing solid tumors. T-DXd showed encouraging ORR, particularly in pts with IHC 3+ expression, durable clinical benefit, and a manageable safety profile in this heavily pretreated population. These interim results show T-DXd to be a potential new Tx option for pts with HER2-expressing solid tumors. Clinical trial information: NCT04482309.

^a Responses in extramammary Paget disease, head and neck cancer, oropharyngeal neoplasm, and salivary gland cancer.^b By investigator assessment per RECIST 1.1. ^c Central assessment of HER2 expression was done retrospectively for pts enrolled based on local testing; 67 pts were not centrally confirmed as IHC 3+ or IHC 2+.