Does menin inhibition have any MHC class II headroom to work with in B-precursor infant ALL? A flow cytometry experiment on samples that already exist
also called MHC-II headroom experiment · CIITA induction in KMT2A::AFF1 blasts · HLA-DR flow under revumenib · menin inhibitor antigen presentation infant ALL
A 2026 paper showed menin inhibitors make myeloid leukaemia cells visible to donor immune cells by switching on a display molecule. This experiment asks whether that molecule is already switched on in infant leukaemia cells, using a standard laboratory stain on samples that are already stored in freezers.
The same thing, for a scientist
Measure surface HLA-DR, HLA-DP and HLA-DQ, and CIITA and HERV transcript levels, on primary KMT2A::AFF1 and other KMT2A-rearranged infant B-ALL blasts at baseline and after 72-96 h exposure to a clinical menin inhibitor, with KMT2A-rearranged AML blasts as the positive comparator in which the effect has been reported [E1]. The question is binary and the reagents are routine: if baseline MHC class II is already high in B-precursor blasts and does not rise, the antigen-presentation arm of the menin-inhibitor graft-versus-leukaemia mechanism has no headroom in this disease, and the rationale for post-transplant menin maintenance in infant ALL must rest on the lineage-independent donor T-cell arm alone. The experiment tests `hyp-menin-inhibition-restores-gvl-only-where-mhc-ii-is-limiting` and is cheap enough that the main cost is sample access.
Design1 deeper
Samples. Cryopreserved primary blasts: (a) KMT2A::AFF1 infant B-ALL at diagnosis, n>=8; (b) other KMT2A-rearranged infant B-ALL, n>=4; (c) post-transplant relapse KMT2A-rearranged infant B-ALL, n>=3 if obtainable - this arm is the one that could create headroom, since MHC class II downregulation is a recognised immune-escape route at post-transplant relapse; (d) KMT2A-rearranged AML, n>=4, as the positive comparator in which MHC-II induction has been reported 1.
Exposure. Clinical menin inhibitor (revumenib or equivalent) at a concentration producing established target engagement in the same culture system, 72-96 h, with vehicle control. A DOT1L inhibitor arm is optional and informative, because it separates menin-specific effects from general reversal of the KMT2A-fusion programme.
Readouts.
| readout | method | what it answers |
|---|---|---|
| surface HLA-DR, HLA-DP, HLA-DQ | flow cytometry, median fluorescence intensity and % positive | is there headroom, and does it fill? |
| CIITA transcript | qPCR | does the transcriptional switch move? |
| HERV transcripts and an interferon-stimulated gene panel | qPCR or RNA-seq | do the UPSTREAM steps of the mechanism occur in B lineage? |
| viability and differentiation markers | flow cytometry | is the culture healthy and is the fusion programme being reversed? |
Controls. Interferon-gamma as a positive control for MHC-II inducibility in each sample - a sample that does not respond to interferon-gamma is not informative about menin inhibition. Normal donor B cells as a constitutive-expression reference. This is the rule-67 spike applied to a cell-biology assay: a negative result is uninterpretable unless the assay has been shown able to return a positive in that same sample.
Reading the result
| baseline MHC-II | rises under menin inhibition? | interpretation |
|---|---|---|
| high | no | hypothesis supported: no headroom in B lineage; maintenance rationale rests on the T-cell arm only |
| low | yes | hypothesis falsified; the Fetsch mechanism transfers to B-precursor disease |
| high | yes | headroom existed above the constitutive level; mechanism transfers and the lineage argument was wrong about magnitude |
| low | no | check whether HERV and interferon-stimulated genes moved. If they did not, the mechanism fails upstream and the lineage argument is the wrong explanation. If they did, the block is at CIITA specifically, which is itself a finding. |
The post-transplant relapse arm is read separately: if those blasts have LOW baseline MHC-II where diagnostic blasts have high, the headroom is created by relapse, and maintenance started before relapse is acting on the wrong cell state - which would argue for a different trial design rather than against the drug.
Why it is worth doing before the trials read out
Five registered post-transplant menin-maintenance studies are recorded in concept-hsct-in-kmt2a-r-leukemia, of which the only randomised one excludes children entirely and the only paediatric-inclusive recruiting one has adverse events as its sole primary outcome. When any of them reports in a lymphoid or mixed population, a null result will be uninterpretable between two explanations: the drug does not prevent relapse, or one arm of its mechanism was never available in that lineage.
This experiment separates those explanations for the cost of a flow panel. It requires no new patients, no new trial and no animal work, and the samples are the ones this graph's collaborators already hold.
| design | Cryopreserved primary blasts from four groups - KMT2A::AFF1 infant B-ALL at diagnosis (n>=8), other KMT2A-rearranged infant B-ALL (n>=4), post-transplant relapse KMT2A-rearranged infant B-ALL (n>=3 if obtainable), and KMT2A-rearranged AML as positive comparator (n>=4) - exposed for 72-96 h to a clinical menin inhibitor at a target-engaging concentration versus vehicle, with an optional DOT1L-inhibitor arm to separate menin-specific from general fusion-programme effects. |
|---|---|
| readout | Surface HLA-DR/DP/DQ by flow cytometry (median fluorescence intensity and percentage positive); CIITA transcript by qPCR; HERV transcripts and an interferon-stimulated gene panel by qPCR or RNA-seq; viability and differentiation markers by flow. |
| controls | Interferon-gamma as a positive control for MHC class II inducibility in EVERY sample - a sample that does not respond to interferon-gamma is uninformative about menin inhibition. Normal donor B cells as a constitutive-expression reference. Vehicle control throughout. This is the project's rule-67 spike principle applied to a cell-biology assay: a negative is uninterpretable unless the assay has been shown able to return a positive in that same sample. |
| cost tier | low |
| timeline | 3-4 months given sample access; the rate-limiting step is obtaining post-transplant relapse material, which may not exist in sufficient quantity and can be dropped without invalidating the primary comparison |
| primary comparison | baseline and post-treatment surface MHC class II in KMT2A::AFF1 infant B-ALL versus KMT2A-rearranged AML |
| why now | Five registered post-transplant menin-maintenance studies exist and none was designed around either arm of this mechanism. When one reports in a lymphoid or mixed population, a null result will be uninterpretable between 'the drug does not prevent relapse' and 'one arm of the mechanism was never available in that lineage'. This experiment separates those for the cost of a flow panel on existing samples. |
decision table
{
"high_baseline_no_rise": "hypothesis supported - no headroom in B lineage; post-transplant menin maintenance rationale in infant ALL rests on the T-cell-intrinsic arm alone",
"low_baseline_rise": "hypothesis falsified - the Fetsch mechanism transfers to B-precursor disease",
"high_baseline_rise": "mechanism transfers above the constitutive level; the lineage argument was wrong about magnitude",
"low_baseline_no_rise": "check HERV and interferon-stimulated genes: if they did not move, the mechanism fails upstream; if they did, the block is at CIITA specifically"
}tests
[ "hyp-menin-inhibition-restores-gvl-only-where-mhc-ii-is-limiting" ]
- A negative result would be uninterpretable without the interferon-gamma control in every sample, and that is the exact failure this project's rule 67 exists to prevent - an instrument returning the answer the hypothesis wanted.
- Cryopreserved primary infant blasts are fragile and their surface phenotype can shift in thaw and short-term culture, so a measured MHC class II level after 96 h in vitro may not be the level on a blast in a child's marrow.
- If the experiment supports the hypothesis, the consequence is that a promising mechanism does not apply to this graph's index disease - which is a useful result and an unwelcome one, and is exactly the kind of finding that does not get published.
- Measuring headroom on diagnostic blasts answers the wrong question if the headroom is created by post-transplant relapse. The most informative arm is the one most likely to be dropped for lack of material.
- Even a fully positive result would establish only that the antigen-presentation arm is available, not that graft-versus-leukaemia operates in this disease at all - and that prior question has never been answered.
- Are post-transplant relapse samples of KMT2A-rearranged infant ALL available in any biobank in sufficient number? This arm is the most informative and the hardest to obtain, and its absence would leave the pre-relapse question answered and the relapse question open.
- Should the exposure arm include a menin inhibitor plus interferon-gamma combination? If MHC-II is already maximal, a combination arm establishes the ceiling and makes a null result interpretable rather than merely negative.
- Does the DOT1L-inhibitor arm separate menin-specific effects from general reversal of the KMT2A-fusion transcriptional programme? If both drugs induce HERVs equally, the effect is a property of the fusion programme and not of the menin interface, which would change the therapeutic argument considerably.
- Would a parallel measurement of MHC class I and antigen-processing machinery be more informative than MHC class II in a B-lineage disease, given that the class II arm may be saturated?
- E1moderate confidence 3 of 5: One strong study, or several smaller consistent ones.paper
Menin inhibition induced CIITA and MHC class II expression in KMT2A-rearranged and NPM1-mutated AML cells in vitro and in vivo through human endogenous retrovirus derepression and interferon-stimulated gene upregulation, sensitising them to T-cell-mediated elimination after allogeneic HCT in mice and enhancing the graft-versus-leukaemia effect in human xenograft models.
Menin inhibition enhances graft-versus-leukemia effects by T-cell activation and endogenous retrovirus induction in AML. · Fetsch V, Schwoebel L, Ozyerli-Goknar E, Stell AV, Punta M, Plenge T, Klaus T, Gupta MK, et al. · Blood 2026What this evidence cannot show
Myeloid models only; no lymphoid model is reported in the abstract, which is precisely the gap this experiment addresses. Mouse allogeneic HCT and human xenograft systems. Only the abstract was read on 2026-09-20 - no PMC record was available - so the specific menin inhibitor, concentrations, exposure durations and the magnitude of MHC-II induction are not known to this entry and the experimental design above specifies its own parameters rather than matching the source.
Evidence that argues against this (1)
- If the abstract-level reading is incomplete and the published paper already includes a lymphoid model, this experiment is partly redundant. The full text should be retrieved before the experiment is run, and the design adjusted to whatever lymphoid data exist - a step this entry cannot take because the paper was not available in full at the time of writing. Inukai T et al. 2006
- E2moderate confidence 3 of 5: One strong study, or several smaller consistent ones.paper
A graft-versus-leukaemia effect after allogeneic transplant has not been clearly evidenced in MLL-rearranged infant leukaemias, whose cells are highly resistant to TRAIL through low surface death-receptor expression in ALL and decoy-receptor expression in AML, and are insensitive to FasL in nearly half of cell lines and most primary cells.
Resistance of infant leukemia with MLL rearrangement to tumor necrosis factor-related apoptosis-inducing ligand: a possible mechanism for poor sensitivity to antitumor immunity. · Inukai T, Zhang X, Goto M, Hirose K, Uno K, Akahane K, Nemoto A, Goi K, et al. · Leukemia 2006What this evidence cannot show
In vitro only, testing death-ligand sensitivity rather than antigen presentation, so it establishes that there is a reason to doubt graft-versus-leukaemia in this disease without bearing directly on the MHC class II question this experiment asks. Published 2006. It is cited here as the motivation for asking the question at all, not as evidence for the experiment's predicted outcome.
Evidence that argues against this (1)
- Graft-versus-leukaemia is demonstrated in paediatric ALL as a population: in 1,619 paediatric CR1/CR2 transplants reported to CIBMTR, acute or chronic GVHD was associated with a lower relapse hazard of 0.49-0.69. If the population-level effect operates in KMT2A-rearranged infant disease too, then the baseline is not as impaired as the 2006 in vitro work suggests and the headroom question is less consequential. Yeshurun M et al. 2019
companion design: class I plus NK ligands here, class II headroom there; the two panels should be run on the same samples
flow cytometry for surface MHC class II at baseline and under menin inhibition, with interferon-gamma as an in-sample positive control
- related to →KMT2A::AFF1 (MLL-AF4), t(4;11)(q21;q23)
primary KMT2A::AFF1 infant B-ALL blasts are the index samples
clinical menin inhibitor exposure arm at a target-engaging concentration
CIITA transcript is a primary readout alongside surface HLA-DR/DP/DQ