Takayuki Yoshino, Maria Di Bartolomeo, Kanwal Pratap Singh Raghav, Toshiki Masuishi, Fotios Loupakis, Hisato Kawakami, Kensei Yamaguchi, Tomohiro Nishina, Zev A. Wainberg, Elena Elez, Javier Rodriguez, Marwan Fakih, Fortunato Ciardiello, Kapil Saxena, Kojiro Kobayashi, Emarjola Bako, Yasuyuki Okuda, Gerold Meinhardt, Axel Grothey, Salvatore Siena

Background: T-DXd is an antibody–drug conjugate of a humanized anti-HER2 antibody bound to a topoisomerase I inhibitor by a cleavable linker. The primary analysis of DESTINY-CRC01 (DS8201-A-J203; NCT03384940), a phase 2, open-label, multicenter study of T-DXd in pts with HER2-expressing mCRC showed promising antitumor activity and a manageable safety profile (cohort A median follow-up [FU], 27.1 weeks; Siena S, ASCO 2020). We present updated longer-term efficacy and safety data.

Methods: Pts had centrally confirmed HER2-expressing, RAS wild-type mCRC that progressed after $2 prior regimens. 6.4 mg/kg of T-DXd was administered every 3 weeks (Q3W) in 3 cohorts (A: HER2 IHC3+ or IHC2+/ISH+; B: IHC2+/ISH- ; C: IHC1+).The primary end point was confirmed objective response rate (ORR) by independent central review in cohort A. Secondary end points were disease control rate (DCR; CR + PR + SD), duration of response (DOR), progression-free survival (PFS), and overall survival (OS).

Results:At data cutoff (Dec 28, 2020), 86 pts (A, 53; B, 15; C, 18) received T-DXd. Median age was 58.5 y (range, 27-79), 53.5% were male, and 90.7% had left colon or rectum cancer. Median prior regimens for metastatic disease was 4 (range, 2-11). All pts had prior irinotecan; 30.2% in cohort A had prior anti-HER2 therapy. Median (m) treatment duration (all pts) was 3.0 mo (95% CI, 2.1-4.1; cohort A, 5.1 mo [95% CI, 3.9-7.6]). In cohort A (median FU, 62.4 weeks), confirmed ORR was 45.3% (24/53 pts; 95% CI, 31.6-59.6), DCR was 83.0% (44/53 pts; 95% CI, 70.2-91.9), mDOR was 7.0 mo (95% CI, 5.8-9.5), mPFS was 6.9 mo (95% CI, 4.1-8.7) with 37 (69.8%) PFS events, and mOS was 15.5 mo (95% CI, 8.8-20.8) with 36 (67.9%) OS events. These results are consistent with the primary analysis. Confirmed ORR was 43.8% (7/16 pts; 95% CI, 19.8-70.1) in pts with prior anti-HER2 therapy, 57.5% (23/40 pts; 95% CI, 40.9-73.0) in pts with IHC3+ status, and 7.7% (1/13 pts; 95% CI, 0.2-36.0) in pts with IHC2+/ISH+ status. In cohorts B and C, mPFS was 2.1 mo (95% CI, 1.4-4.1) and 1.4 mo (95% CI, 1.3-2.1); mOS was 7.3 mo (95% CI, 3.0-NE) and 7.7 mo (95% CI, 2.2-13.9), respectively. Treatment-emergent adverse events (TEAEs) of grade (G) $3 occurred in 65.1% of pts (56/ 86); the most common TEAEs were hematologic and gastrointestinal. TEAEs leading to drug discontinuation occurred in 13 pts (15.1%). 8 pts (9.3%) had interstitial lung disease (ILD) adjudicated by an independent committee as related to T-DXd (4 G2; 1 G3; 3 G5).

Conclusions:T-DXd at 6.4 mg/kg Q3W showed promising activity and durability with longer-term FU in this pt population. The safety profile was consistent with prior results; ILD continues to be recognized as an important identified risk that requires careful monitoring and intervention as needed. These results support continued exploration of TDXd in pts with HER2-overexpressing mCRC.

Clinical trial information: NCT03384940.

Research Sponsor: Daiichi Sankyo, Pharmaceutical/Biotech Company