The parathyroid does not need the rest of the body: deleting menin only there causes neoplasia and hypercalcaemia
also called parathyroid-specific Men1 knockout · PTH-Cre Men1 flox · Men1 heterozygous hypercalcaemia
Scientists deleted the menin gene only in the parathyroid glands of mice, leaving it intact everywhere else. Those mice grew parathyroid tumours and had high blood calcium, which shows the gland goes wrong on its own rather than because of something happening elsewhere.
The same thing, for a scientist
Establishes that parathyroid menin loss is cell-autonomous and sufficient. A floxed Men1 allele was combined with Cre driven by a parathyroid-cell-specific promoter; the resulting mice showed histology consistent with parathyroid neoplasia and systemic hypercalcaemia [E1]. The germline heterozygous model corroborates the endocrine phenotype with numbers: in 220 Men1(+/-) and 94 wild-type mice followed from 3 to 21 months, parathyroid hyperplasia appeared by 9 months and parathyroid adenomas by 15 months, and mice with parathyroid neoplasia were **hypercalcaemic and hypophosphataemic with inappropriately normal serum PTH** [E2]. That biochemical triad is worth noting against the human drug data, where phosphate rises rather than falls.
Why cell-autonomy matters for a systemic drug
A systemic menin inhibitor reaches the parathyroid directly. If parathyroid pathology required a permissive systemic context - hypocalcaemia, renal failure, a second tissue's signal - one could argue the drug's parathyroid exposure is harmless in an otherwise healthy child. 1 closes that argument: deleting menin in the parathyroid alone, with the rest of the mouse wild-type, is sufficient for neoplasia and hypercalcaemia. The gland is a competent target in isolation.
The biochemistry does not match the drug
Men1(+/-) mice with parathyroid neoplasia are hypercalcaemic and hypophosphataemic 2 - the classic primary-hyperparathyroidism pattern, calcium up and phosphate down. On revumenib, corrected calcium rose in only 15% while phosphate rose in 51% and fell in 25%, with creatinine rising in 38% 3. Raised phosphate with raised PTH is the signature of secondary hyperparathyroidism from renal impairment, not of primary parathyroid autonomy.
This is a real and uncomfortable mismatch for the on-target hypothesis, and it should be stated plainly rather than buried: the human biochemical pattern on revumenib looks more like renal secondary hyperparathyroidism than like the mouse Men1 parathyroid phenotype. The counter-argument is that a 2.5-month drug exposure produces secretory disinhibition without the established gland autonomy that drives frank hypercalcaemia, and that renal impairment is common enough in this population to dominate the phosphate column. Both remain live, and the distinguishing measurement - PTH against creatinine and against drug exposure, on and off treatment - has not been made.
| mouse biochemistry | hypercalcaemia + hypophosphataemia + inappropriately normal PTH |
|---|---|
| human drug biochemistry | PTH up 34%, phosphate up 51%, calcium up 15%, creatinine up 38% |
| concordance | partial - the phosphate direction is opposite |
| cell autonomy | established |
models
[ "parathyroid-specific Men1 conditional knockout", "germline Men1(+/-)" ]
- The parathyroid is a competent, cell-autonomous target for a systemic menin inhibitor; no systemic permissive context is needed.
- But the human biochemical pattern on drug does not match the mouse parathyroid phenotype, and a beat that wants the on-target reading has to own that mismatch rather than cite the mouse as if it agreed.
- Hypercalcaemia in a child on a QTc-prolonging drug is a specific, additive cardiac hazard, and calcium is not a protocol-mandated measurement in any of the three lead trials.
- Does the revumenib PTH rise persist after phosphate and creatinine are adjusted for? This is a regression on existing trial data, not a new study.
- What is the serum calcium and phosphate trajectory in the 34 paediatric patients specifically? The label pools them with adults.
- Would a parathyroid-specific Men1 restoration arm show regression of established hyperplasia?
- E1strong confidence 4 of 5: Replicated in peer-reviewed work by more than one group.paper
Parathyroid-gland-specific deletion of Men1 in mice produces parathyroid neoplasia and systemic hypercalcaemia.
Parathyroid gland-specific deletion of the mouse Men1 gene results in parathyroid neoplasia and hypercalcemic hyperparathyroidism. · Libutti SK, Crabtree JS, Lorang D, Burns AL, Mazzanti C, Hewitt SM, et al. · Cancer Research 2003What this evidence cannot show
2003 paper; the Cre driver's specificity and any leakiness are not re-examined here; histology is described as 'consistent with' neoplasia; no PTH values are given in the abstract; no timeline stated.
Evidence that argues against this (1)
- Complete biallelic deletion from development is the maximal exposure; it says nothing about whether partial competitive occupancy of one binding surface for a few months reaches any threshold. Syndax Pharmaceuticals et al. 2026
- E2strong confidence 4 of 5: Replicated in peer-reviewed work by more than one group.paper
Men1(+/-) mice develop parathyroid hyperplasia by 9 months and adenomas by 15 months, and are hypercalcaemic and hypophosphataemic with inappropriately normal PTH.
Multiple endocrine neoplasia type 1 knockout mice develop parathyroid, pancreatic, pituitary and adrenal tumours with hypercalcaemia, hypophosphataemia and hypercorticosteronaemia. · Harding B, Lemos MC, Reed AA, Walls GV, Jeyabalan J, Bowl MR, et al. · Endocrine-Related Cancer 2009What this evidence cannot show
220 heterozygous versus 94 wild-type mice over 3-21 months; germline model; 'inappropriately normal' PTH complicates direct comparison with a human PTH-rise readout.
Evidence that argues against this (1)
- The biochemical direction of phosphate is opposite to what is reported in revumenib-treated patients, where phosphate rises in 51%, which argues the human signal is not the mouse Men1 parathyroid phenotype. Syndax Pharmaceuticals et al. 2026
- E3established confidence 5 of 5: Multiple independent lines of evidence; treated as settled in the field.database
On revumenib, phosphate increased in 51%, calcium corrected increased in 15%, creatinine increased in 38% and intact PTH increased in 34%.
REVUFORJ (revumenib) tablets, for oral use - US Prescribing Information (SPL version 5, published 20 Feb 2026) · Syndax Pharmaceuticals, Inc. · DailyMed / FDA Structured Product Label, setid 6eb3cdbc-0e74-477d-82d6-3bb172d3f63f 2026What this evidence cannot show
Label laboratory table only; no causal attribution, no off-treatment values, no paediatric subgroup.
Evidence that argues against this (1)
- The ziftomenib label carries no calcium, phosphate or PTH row at all, so there is no class comparator for this biochemical pattern. Kura Oncology et al. 2025
- ← related toTCF3::HLF (E2A-HLF), t(17;19)(q22;p13)
Counter-evidence: Inukai 2007 (PMID 17183364) attributes hypercalcaemia in t(17;19) ALL to PTHrP, confirmed in 11 of 16 assessed patients, not to annexin II
Parathyroid-restricted Men1 deletion is sufficient for neoplasia and hypercalcaemia; the gland is a cell-autonomous target
Biochemical mismatch: the mouse Men1 parathyroid phenotype is hypercalcaemia WITH hypophosphataemia, whereas revumenib raises phosphate in 51%; the human pattern resembles renal secondary hyperparathyroidism more than primary parathyroid autonomy
- co-occurs with →Menin is the switch that lets TGF-beta turn parathyroid hormone down - and it works on secretion, not just growth
Growth arm and secretion arm of the same parathyroid menin function; only the secretion arm operates on a timescale compatible with a 2.5-month drug exposure