Data Originally Presented at SABCS 2020 With an Encore at Miami Breast 2021

Additional follow-up from DESTINY-Breast01—the study supporting accelerated approval of ENHERTU (5.4 mg/kg,
N=184)—June 8, 2020 data cutoff1

Durable response continued with longer duration of follow-up, median 20.5 months
(range: 0.7-31.4)

  • 20.1% of patients remained on treatment (n=37/184)

61.4% ORRa
(n=113/184; 95% CI: 54.0, 68.5)
6.5% CR (n=12) + 54.9% PR (n=101)

20.8-month mDORb
(n=113; 95% CI: 15.0, NE)

19.4-month mPFSc
(95% CI: 14.1, NE)

mOS was immature at time of analysis due to number of events at data cutoff

  • Maturity was estimated at 35% (n=65/184); 65% (n=119/184) were censored
  • Additional follow-up required for more mature OS data

Exploratory landmark OS analyses

  • Estimated 12-month landmark OS was 85% (95% CI: 79, 90)
  • Estimated 18-month landmark OS was 74% (95% CI: 67, 80)

ENHERTU received accelerated approval from FDA based on tumor response rate and duration of response. FDA has not reviewed these additional ORR, DOR, PFS, and OS data. Multiple confirmatory Phase 3 studies are underway.2

Safety evaluated with longer treatment duration, median 10.1 months (range: 0.7-29.5)d

  • 99.5% any TEAE (n=183)
  • 61.4% Grade ≥3 TEAE (n=113)
  • Dose adjustments due to TEAEs
    • 18.5% discontinuation (n=34)
    • 40.8% dose interruption (n=75)
    • 23.9% dose reduction (n=44)
  • 5.4% of TEAEs associated with death
    • TEAEs associated with 1 fatal outcome each: respiratory failure, acute respiratory failure, disease progression, general physical health deterioration, lymphangitis, pneumonia, pneumonitis, shock hemorrhagic
    • 1 patient had 2 TEAEs associated with death: acute kidney injury and acute hepatic failure

Drug-related ILD/pneumonitis occurred in 15.2% of patients (n=28/184)

  • 3 new cases of ENHERTU-related ILD as determined by an independent adjudication committee were reported
    • One Grade 1, one Grade 2, one Grade 5
  • 2 cases were pending adjudication at data cutoff

There was 1 additional case of LVEF decrease (Grade 2) and no new TEAEs of cardiac
failure reported

  • 4 total events of LVEF decrease (three Grade 2 and one Grade 3)
  • 2 total cardiac failures (one Grade 1 and one Grade 2) with no LVEF decrease were observed during treatment
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aORR defined as CR+PR per RECIST v1.1 in the ITT population as evaluated by ICR.3,4 bMedian DOR based on Kaplan-Meier estimate.3 cDisease progression was assessed using modified RECIST v1.1.4 dRelationship to study drug was determined by the treating investigator.1

CI, confidence interval; CR, complete response; DOR, duration of response; FDA, Food and Drug Administration; ICR, independent central review; ILD, interstitial lung disease; ITT, intent-to-treat; LVEF, left ventricular ejection fraction; mDOR, median duration of response; mOS, median overall survival; mPFS, median progression-free survival; NE, not evaluable; ORR, objective response rate; OS, overall survival; PFS, progression-free survival; PR, partial response; RECIST, Response Evaluation Criteria in Solid Tumors; TEAE, treatment-emergent adverse event.