Zoledronic acid against the osteoclast: a bone-marrow-niche target, but not tested in infant KMT2A-rearranged disease
also called zoledronic acid B-ALL · osteoclast target leukaemia · bisphosphonate leukaemia · RANKL niche ALL
Leukaemia makes bone-eating cells more active, and those cells in turn release factors that help the leukaemia grow. Blocking them with a bisphosphonate extended survival in mice and reversed the bone damage, and three children tolerated the drug safely during chemotherapy - but none of this work used infant KMT2A-rearranged leukaemia.
The same thing, for a scientist
A second paper the graph held as unreadable, retrieved in full from Europe PMC by this beat. In a murine BCR::ABL1-positive B-ALL syngeneic model, zoledronic acid alone significantly extended survival against vehicle, and improved on imatinib or dasatinib alone when combined with them, including in a high-disease-burden setting (34.2 +/- 17.12% marrow involvement) [E1]. In the ALL-84 patient-derived xenograft, derived from a 14-year-old with relapsed B-ALL expressing high RANKL, zoledronic acid improved survival both as a single agent and added to vincristine/dexamethasone/asparaginase induction, and after induction [E1]. Micro-CT confirmed reversal of trabecular bone loss and cortical thinning and TRAP staining a reduction in osteoclasts; zoledronic acid after induction did not promote relapse [E1]. Mechanistically, conditioned medium from differentiated osteoclasts increased B-ALL proliferation and reduced apoptosis, with 30 differentially expressed genes and upregulation of p53 signalling, cell cycle, cell adhesion and ECM-receptor pathways [E1]. Three children with bone-symptomatic B-ALL and vertebral crush fractures received zoledronic acid during induction or consolidation without significant adverse effects [E2]. **The relevance to this beat is explicitly limited**: no model here is KMT2A-rearranged, none is an infant, and the drug is a bisphosphonate given to patients whose skeleton is still forming.
Why this is recorded as a bounded rejection as much as a finding
A reader would expect a 2025 Kotecha-group paper titled 'Targeting osteoclasts for treatment of high-risk B-cell acute lymphoblastic leukemia' to be cited in an infant KMT2A-rearranged beat. It is not directly applicable, and the reasons should be on the record so that the next cycle does not re-read it from scratch:
- The syngeneic model is BCR::ABL1-positive, a different fusion with a different niche biology and a different standard therapy.
- The PDX (ALL-84) is from a 14-year-old with relapsed B-ALL, selected for high RANKL expression.
- The clinical vignettes are three children with a bone-symptomatic phenotype and vertebral crush fractures, which is not the usual presentation of infant KMT2A-rearranged ALL.
- Bisphosphonates deposit in bone with a half-life measured in years. In a patient who has not yet walked, the long-term skeletal consequence is unstudied.
What would change that judgement: a KMT2A-rearranged infant PDX experiment, or evidence that infant KMT2A-rearranged blasts express RANKL or respond to osteoclast-conditioned medium.
What does carry across
The mechanistic half is fusion-agnostic and therefore does plausibly transfer: soluble factors from osteoclasts increase B-ALL proliferation (higher cell numbers, more S/G2/M) and reduce apoptosis, with proteomics of osteoclast conditioned medium showing proteasome, ACP5, cathepsin D, T-complex protein 1, Arp2/3, V-ATPase and coatomer protein 1 1. If that crosstalk operates on KMT2A-rearranged blasts too, the marrow niche is a shared vulnerability. The experiment that tests it is small: osteoclast conditioned medium on infant KMT2A-rearranged PDX cells.
There is also a safety-relevant read-across in the opposite direction. Infant ALL survivors carry documented bone and endocrine late effects, and this graph already holds entries on growth and endocrine late effects. A drug that reverses leukaemia-induced bone loss is interesting for that reason independent of any anti-leukaemic effect, and the fact that it did not promote relapse when given after induction 1 is the safety observation that makes such a use conceivable.
| modality | bisphosphonate (osteoclast inhibition), bone-marrow niche directed |
|---|---|
| agent | zoledronic acid |
| stage | preclinical plus three clinical safety vignettes |
| applicability to this beat | indirect; no KMT2A-rearranged model, no infant, different fusion |
| source pmid | 40016188 |
| retrieved from | Europe PMC full text PMC11868389, 2026-09-19 |
models used
[ "murine BCR::ABL1+ B-ALL syngeneic", "ALL-84 PDX from a 14-year-old with relapsed B-ALL, high RANKL" ]
what would make it applicable
[ "osteoclast-conditioned-medium response in infant KMT2A-r PDX cells", "RANKL expression in infant KMT2A-r blasts", "a KMT2A-r infant PDX zoledronic acid experiment" ]
- Bisphosphonates deposit in bone and release slowly over years, so an exposure at nine months of age is an exposure through the whole of growth, and no infant cohort has been followed for it.
- Suppressing osteoclasts suppresses bone remodelling, which is how a growing skeleton lengthens and remodels; the essential-function toxicity here is growth itself.
- The niche effect is not fusion-specific, so if it works it works partly by slowing leukaemia rather than killing it, and slowing a disease with a 60% two-year relapse rate buys time rather than cure.
- Osteonecrosis of the jaw and atypical femoral fracture are late bisphosphonate toxicities with latencies longer than any of this work's follow-up.
- Do infant KMT2A-rearranged blasts respond to osteoclast-conditioned medium the way BCR::ABL1-positive blasts do? This is a one-week experiment and would decide whether the niche target transfers.
- Do infant KMT2A-rearranged blasts express RANKL, and does leukaemia-induced bone loss occur at all in a skeleton that has not yet borne weight?
- Is there any safe bisphosphonate exposure in a patient under one year of age, given a skeletal half-life measured in years?
- E1strong confidence 4 of 5: Replicated in peer-reviewed work by more than one group.paper
Zoledronic acid extended survival in a murine BCR::ABL1-positive B-ALL syngeneic model alone and combined with imatinib or dasatinib, extended survival in the ALL-84 relapsed-B-ALL patient-derived xenograft alone, with VXL induction and after induction, reversed trabecular bone loss and cortical thinning on micro-CT, reduced TRAP-positive osteoclasts, did not promote relapse when given post-induction, and osteoclast-conditioned medium increased B-ALL proliferation and reduced apoptosis.
Targeting osteoclasts for treatment of high-risk B-cell acute lymphoblastic leukemia. · Kotecha RS, Trinder SM, Hughes AM, Mullin BH, Rashid S, Yuan J, et al. · Blood Cancer J 2025What this evidence cannot show
No model is KMT2A-rearranged and none is an infant. The syngeneic model is BCR::ABL1-positive; the PDX is from a 14-year-old with relapsed disease selected for high RANKL. Mouse group sizes 8-10. The mechanistic work uses the RAW264.7 murine macrophage line as the osteoclast source, not primary human osteoclasts. The paper carried no abstract in PubMed or Europe PMC; the full text was retrieved from Europe PMC (PMC11868389) and read in full by this beat on 2026-09-19.
Evidence that argues against this (2)
- THE PAPER'S OWN DATA, and the same paper states the confound. Dasatinib itself inhibits osteoclast formation and activity, so part of the combination effect in the BCR::ABL1 arms is a redundant mechanism; the paper reports zoledronic acid as the more potent osteoclast inhibitor, which sharpens rather than removes the confound. Verified in the PMC full text on 2026-09-20: the authors write that 'Dasatinib is known to dysregulate bone remodeling by inhibiting osteoclast activity and abrogating osteoclast formation', observe it in their own study, and attribute it to two prior papers. Those prior papers were not cited here; the primary one is now the note below. Kotecha RS et al. 2025
- INDEPENDENT SOURCE, added 2026-09-20 by the Q40 counter-evidence quality sweep, and it makes the confound larger than the same-source note allows. In Sprague-Dawley rats dosed for 4-12 weeks, dasatinib alone increased trabecular bone volume and thickness AT LEVELS COMPARABLE WITH the zoledronic-acid arm of the same experiment, with decreased osteoclast number and surface and decreased serum CTX-1, and no change in osteoblast markers. A head-to-head in a model of physiologic turnover therefore does NOT show dasatinib to be the weaker osteoclast inhibitor, which is the framing the index paper's supplementary comparison supports. The redundancy in the BCR::ABL1 combination arms is correspondingly harder to dismiss. Vandyke K et al. 2010
- E2weak confidence 2 of 5: Preliminary, small, indirect, or not yet peer reviewed.paper
Three children with bone-symptomatic B-ALL, diffuse marrow infiltration and multi-level vertebral body crush fractures received zoledronic acid concurrently during induction or consolidation, and in all three it was well tolerated without significant adverse effects.
Targeting osteoclasts for treatment of high-risk B-cell acute lymphoblastic leukemia. · Kotecha RS, Trinder SM, Hughes AM, Mullin BH, Rashid S, Yuan J, et al. · Blood Cancer J 2025What this evidence cannot show
Three clinical vignettes, reported as feasibility and safety only. No efficacy claim. All had a bone-symptomatic phenotype, which selects for patients whose skeleton was already damaged and who therefore had the clearest indication. Ages not stated in the main text read by this beat; none is described as an infant. No narrative detail is reproduced here.
Evidence that argues against this (1)
- Three tolerated exposures cannot bound the rate of osteonecrosis of the jaw, acute-phase reactions, hypocalcaemia or long-term growth effects of a bisphosphonate in a growing skeleton, and the drug's skeletal half-life means adverse effects could appear years after the cohort's follow-up ends. Stutterheim J et al. 2025
- E3strong confidence 4 of 5: Replicated in peer-reviewed work by more than one group.review
Infants with KMT2A-rearranged ALL are treated with intensive chemotherapy whose long-term complications occur across nearly all organ systems, and current knowledge of survivors' quality of life is described as extremely limited.
KMT2A-rearranged acute lymphoblastic leukemia in infants: current progress and challenges. · Stutterheim J, Van der Sluis IM, Vrenken KS, Pieters R, Stam RW · Haematologica 2025What this evidence cannot show
A narrative review's characterisation of the late-effects literature rather than a measurement. Read in the open-access full text at PMC12399962.
Evidence that argues against this (1)
- If late-effect data are extremely limited, then the claim that infant survivors have a bone problem large enough to justify a bisphosphonate is itself unquantified, and the case for read-across rests on plausibility. Kotecha RS et al. 2025
PMID 40016188 is now readable in full via Europe PMC PMC11868389
- related to →KMT2A-rearranged acute lymphoblastic leukaemia
osteoclast-leukaemia crosstalk proposed as fusion-agnostic; not tested in any KMT2A-rearranged model
a bone-directed agent read against infant skeletal late effects
osteoclast targeting in high-risk B-ALL
the dasatinib osteoclast confound had no primary source; PMID 20225261 added and the confound is larger than stated