Who holds the data and samples we cannot generate ourselves — an access map

Archival and retrievability of the breakpoint sequences is inferred from the assay methodology, not stated. This is the single unverified link in the proposal and must be confirmed first.

• Changes the shape of the Interfant ask. This entry treats the Interfant resource as archival and frames the gating unknown as 'whether the sequences were archived'. The consortium is not archival: Interfant-21 (NCT05327894) has been RECRUITING since December 2022, sponsored by the Princess Maxima Center with the University of Milano-Bicocca and Amgen Europe B.V., with an estimated 160 infants under one year with KMT2A-rearranged ALL or MPAL, phase 3, non-randomised, blinatumomab-based, primary completion September 2027. Two consequences. First, the higher-value request is prospective, not retrospective: asking that patient-specific genomic breakpoint sequences generated as MRD targets in Interfant-21 be retained and annotated costs the consortium almost nothing and removes the archival uncertainty entirely for the next cohort, whereas the Interfant-06 archive question may simply have no good answer. Second, the registry record lists no menin inhibitor among Interfant-21's interventions, so this access route supplies infant material and outcome data but not menin-inhibitor exposure; for that, the map should point at COG AALL2121 (NCT05761171) and TINI 2 (NCT05848687) instead. Caveat: a registry record summarises a protocol and does not establish what molecular data the trial office actually retains, nor its data-sharing policy. Read: full registry record, retrieved 2026-09-18. Princess Maxima Center for Pediatric Oncology; University of Milano Bicocca; Amgen Europe B.V. 2026

Referral cohort with geographic and ascertainment bias; no published data-sharing policy and no verified public deposition of the underlying sequences.

• Adds a specific, citable open-data resource this map does not list, and with it a correction to the 'open now' section. The map's open tier names St. Jude Cloud and TARGET generically. The concrete item worth naming is the PCGP infant MLL-rearranged whole-genome cohort: Andersson et al. sequenced 65 infants (47 MLL-rearranged, 18 non-MLL-rearranged) and 20 older children with MLL-rearranged leukaemia by whole-genome, exome, RNA and targeted DNA sequencing, reporting a mean of 1.3 non-silent mutations in the predominant leukaemic clone - among the lowest somatic mutation burdens of any sequenced cancer - with subclonal kinase-PI3K-RAS pathway mutations in 47% of cases that were frequently lost at relapse. This is the only infant KMT2A-rearranged whole-genome cohort of any size identified in this survey, and it is reachable under a data-access agreement rather than through a collaboration. The counter-evidential point for this map is that its central strategic claim - that access, not hypothesis quality, is the binding constraint - is weaker than stated for the genomic questions: for those, the binding constraint is cohort size and mutation burden, not permission. Forty-seven genomes at 1.3 mutations per clone will not support a recurrence analysis of regulatory variants however freely they are shared. Caveats: the cohort is a decade old, sequencing depth and pipelines are of their time, and the abstract does not state what fraction is whole-genome rather than exome. Read: abstract only. Andersson AK et al. 2015

Retrieved and verified by a worker agent in this same survey cycle from registry records, which are sponsor-submitted, can lag reality and state planned rather than achieved enrolment. Minimum age in a registry entry does not guarantee that infants were actually enrolled.

• Qualifies the entry's most operationally load-bearing claim. This item is cited to establish that an infant-eligible menin-inhibitor cohort exists and is therefore a target for sample access. The full AALL2121 registry record shows that the obvious correlative work on that cohort is already protocol-specified: exploratory outcome measures include paired pre- and post-treatment RNA-seq of the KMT2A-R transcriptional programme, with principal component analysis and gene-set enrichment correlated to clinical response and pharmacokinetics, and menin occupancy by CUT&RUN with CUT&Tag for histone modifications and protein complexes, also correlated to response. Three further eligibility facts change what this cohort can supply: the primary MRD endpoint is limited to patients 6 months and older at enrolment, with under-6-month patients appearing only as a descriptive exploratory outcome; eligibility runs to under 6 years with diagnosis under 2 years, so 'infant' in the trial's sense is broader than under 12 months; and patients previously treated with revumenib are excluded, so the cohort yields no post-menin-inhibitor resistance material. The practical revision to this access map: AALL2121 is a gated resource whose menin-displacement and transcriptional correlatives are already allocated, and the tractable ask is an orthogonal assay the protocol does not list, not the assays it does. Caveat: outcome measures state planned analyses, not who performs them or whether specimen aliquots remain; a COG investigator could still confirm capacity. Read: full registry record including eligibility, detailed description and all outcome measures, retrieved 2026-09-18. Children's Oncology Group 2026

This cohort is one programme's registration arm; it characterises the field's centre of gravity rather than proving scarcity of infant material across all trials.

• The scarcity conclusion is right and understated. Median ages of 66 to 69 mean the combination cohorts contain essentially no paediatric material at all, so the constraint is not that infant-relevant samples are scarce but that for the combination regimens they do not yet exist — which makes prospective collection, not negotiation for access, the operative plan. Journal of Clinical Oncology 2025