Briefing · From the Watchtower
Merck and Daiichi Sankyo withdraw I-DXd accelerated-approval BLA
The sponsors ended the US accelerated-approval filing after FDA discussions, while the randomized Phase 3 survival trial continues.[1][2]
What happened
Merck announced on 25 September 2026 that it and Daiichi Sankyo had voluntarily withdrawn the US accelerated-approval biologics license application for ifinatamab deruxtecan, or I-DXd, in adults with extensive-stage small cell lung cancer whose disease progressed on or after platinum chemotherapy.[1] The sponsors said discussions with the US Food and Drug Administration concluded that the supporting package, including Phase 2 IDeate-Lung01, did not satisfy the requirements for accelerated approval in that indication.[1]
The withdrawal ends this application.[1] It does not stop I-DXd development: Merck said enrollment continues in Phase 3 IDeate-Lung02, while Daiichi Sankyo described enrollment as near completion and tied any future filing to that trial's results.[1] This accelerated-approval application is no longer under FDA review; the sponsors did not specify the pathway or timing of any future filing.[1]
Why it matters
IDeate-Lung02 is a randomized study of I-DXd versus treatment of physician's choice in subjects with relapsed small cell lung cancer.[2] The open-label Phase 3 study has an estimated enrollment of 540, with overall survival as the primary outcome; objective response and progression-free survival are secondary outcomes.[2]
That endpoint hierarchy changes the competitive question. A response signal cannot answer whether I-DXd extends survival against physician-choice chemotherapy in this trial.[2] Prognyx's reading is that response depth and duration remain informative, while a development or partnering case without credible survival evidence now carries greater regulatory risk in previously treated ES-SCLC after this withdrawal.[1][2]
A positive overall-survival result would support a future filing with randomized evidence against active treatments in the study population.[1][2] A result that improves response rate or progression-free survival without improving overall survival would leave the trial short on its primary outcome.[2]
What to watch next
The ClinicalTrials.gov record, updated on 6 August 2026, lists IDeate-Lung02 as recruiting and estimates primary completion on 30 January 2028.[2] It estimates study completion on 1 December 2029.[2] These are registry planning dates, rather than announced readout or FDA decision dates.[2]
Daiichi Sankyo said a future filing would depend on IDeate-Lung02 results.[1]
The now-what
For the sponsors, the immediate task is to protect trial execution and preserve the interpretability of overall survival. The public record supports continued enrollment and ongoing development.[1][2] The accelerated-approval application was voluntarily withdrawn, while patient enrollment continues in the Phase 3 trial.[1][2]
IDeate-Lung02 is a randomized Phase 3 study of ifinatamab deruxtecan versus treatment of physician's choice in relapsed small cell lung cancer.[2]
Overall survival is defined as the time from randomization to death due to any cause.[2] The estimated primary completion date is 30 January 2028.[2]
What Prognyx could not verify
Prognyx could not verify an independent FDA decision document, an IDeate-Lung02 readout date, a future BLA filing date, or the trial's statistical design, powering assumptions or event threshold. No probability or timing of success can be inferred from the public information available as of 28 September 2026.
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Questions this briefing answers
Does the BLA withdrawal mean I-DXd development has stopped?
No. Merck said enrollment continues in Phase 3 IDeate-Lung02, and Daiichi Sankyo described enrollment as near completion.[1] The ClinicalTrials.gov record lists the study as recruiting.[2]
What evidence could support a future I-DXd filing in relapsed small cell lung cancer?
Daiichi Sankyo said a future filing would depend on IDeate-Lung02 results.[1] The randomized Phase 3 trial compares I-DXd with physician-choice chemotherapy and has overall survival as its primary outcome.[2]
Sources: every claim traces to the primary record
How this briefing was produced: Drafted and audited by the Prognyx engine against the primary sources cited above, then published automatically for clearing the audit threshold set by Rali Filali. Below that threshold, a briefing is not published. The full method.
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