3076 Background: HM781-36B is a pan-HER tyrosine kinase inhibitor, which showed a potent activity against the gefitinib- or erlotinib-resistant, EGFR L858R/T790M double mutant cells. A phase I study was conducted to determine the MTD, pharmacokinetics, and antitumor activity. Methods: Eligible pts had advanced malignancies refractory to standard therapies. Standard 3+3 scheme was used in the dose escalation part, and additional 12 pts were enrolled in the expansion cohort of molecular enrichment. Results: In dose-escalation part, 43 pts (median age: 55 yrs (range 25-82), M:F=25:18, ECOG PS 0/1/2/3: 23/17/2/1, median prior chemotherapy: 4) were treated. DLTs were G3 diarrheas in 5 pts, one at 12 mg, 16 mg, 24 mg, and two at 32 mg. The MTD was determined as 24mg. The most common drug-related adverse events were diarrhea, stomatitis, rash, pruritus, and anorexia. Among 41 evaluable pts, 4 pts achieved PR (1 unconfirmed, duration of response: 11.9 mo, 7.07 mo+, 4.5 mo+), and 19 pts had SD. Two of 4 PR pts were Her2-positive breast cancer pts. The median duration of treatment in pts with PR or SD was 3.87 (2.47- 15.17) months. In the dose range of 0.5 to 24 mg, it showed linear pharmacokinetics proportional to dose-escalation, relatively short half-life, and little accumulation. Additional 12 pts in the expansion cohort are under treatment at 24 mg (6 pts: EGFR-mutant NSCLC, 3 pts: Her2-positive gastric cancer, 2 pts: Her2-positive breast cancer, 1 pt: rectal cancer). Conclusions: HM781-36B was safe and well tolerable in advanced solid tumors. Preliminary evidence of anticancer activity has been observed. Updated data will be presented at the meeting.
Population Pharmacokinetics of Trastuzumab Deruxtecan in Patients With HER2‐Positive Breast Cancer and Other Solid Tumors