Oncofusion

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Drugmoderate confidence 3 of 5: One strong study, or several smaller consistent ones.Q53-transplant

Melphalan - the third agent in Interfant-06 conditioning, dosed per square metre in babies who are dosed per kilogram for everything else in the same week

also called melphalan · L-PAM · L-phenylalanine mustard · phenylalanine mustard · sarcolysin · L-sarcolysin · MEL · Alkeran (trade name) · Evomela (propylene-glycol-free trade name) · nitrogen mustard (class)

Melphalan is the last drug given before the donor cells go in, on the day before transplant. Its main injury is to the lining of the mouth and gut, and there is evidence that giving too much of it makes graft-versus-host disease more likely.

The same thing, for a scientist

Melphalan is a bifunctional nitrogen-mustard alkylator given as a single 140 mg/m2 dose on day -1 of the Interfant-06 conditioning regimen, after four days of oral busulfan and two of cyclophosphamide [E1]. Its dose-limiting toxicity is mucosal rather than hepatic, which is why it is often preferred to busulfan as a conditioning backbone in T-cell-depleted settings [E2]. That mucosal injury is not merely unpleasant: in 85 paediatric alpha/beta T-cell-depleted haploidentical transplants, melphalan exposure above the cohort median of 6.81 mg*h/L was associated with a higher incidence of acute graft-versus-host disease, consistent with mucosal damage initiating alloreactivity [E2]. The same study found that dose adjustment for obesity systematically UNDERexposed those patients, and that a separate adjustment was applied at age under 2 years - the clearest published acknowledgement that a body-surface-area dose does not translate to an infant.

Go deeper
Where melphalan sits in this disease

One dose, 140 mg/m2 intravenously, on day -1 1. The protocol's handling instructions are unusually specific - 'Melphalan is to be applied at least 3 hours after dissolution as an one-hour infusion. MEL may only be dissolved in sodium chloride infusion, and may not be mixed with glucose' - because melphalan hydrolyses rapidly in solution and loses potency.

The choice of melphalan as the third agent is a protocol-level decision that was never tested against the alternative. JPLSG MLL-10, the other large infant protocol of the same era, used etoposide as its third agent alongside targeted busulfan and cyclophosphamide, and reported 3-year EFS of 56.8% in high-risk KMT2A-rearranged infants 3. No trial has compared the two third agents in infants, and drug-etoposide already exists in this graph as a frontline agent without its conditioning role recorded.

The mucositis-to-GVHD link, which is the part that generalises

Melphalan is chosen in T-cell-depleted transplant because its organ toxicity is lower than busulfan's or TBI's, at the cost of significant mucosal injury 2. The Dvorak analysis tested the obvious consequence - that mucosal injury initiates alloreactivity - and found it: above the cohort median exposure of 6.81 mg*h/L, acute GVHD was more frequent, and engraftment syndrome was strongly associated with subsequent grade II-IV (41.4% vs 17.3%) and grade III-IV (34.5% vs 8.5%) acute GVHD 2.

That matters for the graft-versus-leukaemia argument in concept-graft-versus-leukaemia-in-kmt2a-rearranged-infant-leukaemia. If conditioning intensity partly causes GVHD, then a comparison of GVHD-positive and GVHD-negative patients is confounded by how much alkylator they absorbed, and the GVL effect inferred from that comparison is partly a conditioning effect wearing an immunological name.

The infant dosing problem, stated by the study that hit it

In the Dvorak cohort, 61.2% received 140 mg/m2 on actual body weight; 'others received a dose adjusted for obesity or age <2 years' 2. Two populations therefore fall outside the standard body-surface-area calculation and are handled by local convention.

And the direction of the obesity adjustment was wrong: the PK model predicted lower melphalan exposure in obese patients dosed on adjusted ideal body weight (p=0.02), 'suggesting overcorrection of the dose' 2. A correction applied on physiological reasoning, in the absence of exposure data, moved patients out of the target window rather than into it. There is no equivalent published test of the age-under-2 adjustment, so the infant correction is in exactly the position the obesity correction was in before it was measured. See concept-weight-versus-bsa-dosing-in-infant-conditioning.

Facts and figures
targetDNA - bifunctional nitrogen-mustard alkylation forming interstrand cross-links, chiefly at guanine N7. Melphalan enters cells on the LAT1/SLC7A5 large neutral amino-acid transporter because it is a phenylalanine conjugate; no transporter node exists in this graph.
modalitysmall molecule, bifunctional nitrogen-mustard alkylator; directly reactive, not a prodrug
role in this diseasethird agent of the Interfant-06 irradiation-free conditioning regimen, single 140 mg/m2 dose on day -1
interfant06 conditioning dose140 mg/m2 i.v. over one hour on day -1, at least 3 hours after dissolution, in sodium chloride only
dose limiting toxicitymucosal (oropharyngeal and gastrointestinal mucositis) rather than hepatic
exposure gvhd relationshipabove a median predicted exposure of 6.81 mg*h/L, higher incidence of acute GVHD in paediatric alpha/beta T-cell-depleted haploidentical HCT
vocabularies searchedPubMed [tiab] counts on 2026-09-20: melphalan OR L-PAM OR phenylalanine mustard OR sarcolysin 9,616; Alkeran 102; Evomela 17. The generic name dominates; trade names add nothing material.
infant specific
[
  "Dosed on BODY SURFACE AREA in a regimen whose other two cytotoxics are dosed on body WEIGHT",
  "A separate dose adjustment is applied at age under 2 years in at least one prospective paediatric programme, with no published exposure validation",
  "The analogous obesity adjustment in the same cohort OVERcorrected, producing significantly lower exposure - a warning about unvalidated physiological corrections",
  "Interfant-06 gives no melphalan dose modification for age or weight at all"
]
key ae
[
  "severe mucositis",
  "myelosuppression",
  "nausea and vomiting",
  "acute GVHD risk at high exposure",
  "renal impairment (excretion is partly renal)",
  "secondary malignancy (alkylator class)",
  "hypersensitivity, including to the propylene-glycol vehicle of the older formulation"
]
resistance
[
  "glutathione S-transferase conjugation and elevated intracellular glutathione",
  "reduced LAT1/SLC7A5-mediated uptake",
  "enhanced interstrand cross-link repair",
  "no KMT2A-rearrangement-specific melphalan resistance measurement was found by this beat"
]
How this could bite us back
  • The toxicity that makes melphalan attractive is also the toxicity that raises GVHD. Choosing it over busulfan trades hepatic injury for mucosal injury, and mucosal injury is a plausible initiator of the alloreactivity that then has to be suppressed for months.
  • An unvalidated infant dose adjustment is worse than none, because it looks like care. The matched case in the same dataset - obesity - was corrected on physiological reasoning and moved patients the wrong way by a statistically detectable amount.
  • One dose, no monitoring, no rescue. Unlike busulfan there is no established melphalan therapeutic drug monitoring in this setting, so an infant with atypical clearance receives a single unrecoverable exposure on the day before the graft.
  • Alkylator-on-alkylator: melphalan is given after four days of busulfan and two of cyclophosphamide. The regimen's cumulative interstrand cross-link burden is never measured as a whole, and second-malignancy risk is a property of the total, not of any component.
  • Renal excretion in a baby whose glomerular filtration rate is still maturing means the same mg/m2 dose produces a different exposure at three months and at eleven months, and the protocol treats the first year as one category.
Still open
  1. Is the age-under-2 melphalan dose adjustment right in direction and magnitude? The obesity adjustment in the same cohort was measured and found to overcorrect; the infant adjustment has never been measured at all.
  2. Melphalan or etoposide as the third agent in infant conditioning? Interfant-06 chose one and JPLSG MLL-10 the other, both with defensible reasoning and neither with a comparison.
  3. If high melphalan exposure raises acute GVHD, how much of the graft-versus-leukaemia effect attributed to donor immunity in transplanted infants is downstream of alkylator-induced mucosal injury?
  4. Does the LAT1/SLC7A5 dependence of melphalan uptake vary with lineage or with the KMT2A-rearranged transcriptional programme, which is unusually stem-like? This is directly testable in the infant ALL cell lines this graph already lists.
Every source behind this entry (3)
  1. E1established confidence 5 of 5: Multiple independent lines of evidence; treated as settled in the field.book

    Interfant-06 conditioning gives melphalan 140 mg/m2 intravenously as a one-hour infusion on day -1, at least three hours after dissolution, dissolved only in sodium chloride and never in glucose, following oral busulfan on days -7 to -4 and cyclophosphamide on days -3 and -2.

    INTERFANT-06: International collaborative treatment protocol for infants under one year with acute lymphoblastic or biphenotypic leukemia (protocol document, SKION version 01, April 2006) · Pieters R, de Lorenzo P, Valsecchi MG, Peters C, and the Interfant-06 study group · Interfant-06 study group / SKION protocol document 2006
    What this evidence cannot show

    The full protocol PDF was retrieved and chapter 6.5 read directly on 2026-09-20. This is the 2006 SKION version of the protocol document and states intent rather than practice; no published report of the Interfant-06 transplanted subgroup describes what conditioning was actually delivered, how many infants received the full melphalan dose, or what the mucositis burden was. The protocol gives no melphalan dose modification for age or weight anywhere in the conditioning chapter.

    Evidence that argues against this (1)
    • The competing infant protocol did not use melphalan at all. JPLSG MLL-10's protocol-specified conditioning was individualised targeted busulfan, ETOPOSIDE and cyclophosphamide in 38 of 43 first-remission transplants. The third agent in infant conditioning is therefore a genuine open choice between two large protocols, not a settled component, and no head-to-head comparison exists. Takachi T et al. 2021
  2. E2moderate confidence 3 of 5: One strong study, or several smaller consistent ones.paper

    In 85 paediatric patients undergoing alpha/beta T-cell-depleted haploidentical transplantation with melphalan-based conditioning, melphalan exposure above the cohort median of 6.81 mg*h/L was associated with increased acute graft-versus-host disease; 61.2% received 140 mg/m2 on actual body weight while others received a dose adjusted for obesity or age under 2 years; and the obesity adjustment produced significantly LOWER predicted exposure (p=0.02), indicating overcorrection.

    High Melphalan Exposure Increases the Risk of Graft-Versus-Host Disease in Pediatric Patients Undergoing Alpha-Beta T-Cell Depleted Haploidentical Transplantation. · Dvorak CC, Cho S, Salinas Cisneros G, Higham CS, Chu J, Winestone LE, Temple WC, Kharbanda S, et al. · Transplantation and Cellular Therapy 2025
    PMID 40185404DOI
    What this evidence cannot show

    85 patients across three centres on two prospective trials, analysed retrospectively by median split of a MODEL-PREDICTED exposure rather than a measured one. The setting is alpha/beta T-cell-depleted haploidentical transplantation, which is not the Interfant-06 setting: GVHD biology differs substantially between a T-cell-depleted haploidentical graft and an unmanipulated marrow from a matched donor with ciclosporin and methotrexate prophylaxis. The exposure threshold of 6.81 mg*h/L is the cohort median, not a validated cut-point. Median age is not infant; the age-under-2 subgroup is mentioned but not analysed separately.

    Evidence that argues against this (1)
    • The same study found no impact of melphalan exposure on immunologic rejection, and the strongest predictor of chronic GVHD in it was prior acute GVHD grade (66.7% after grade II-IV versus 0% after grade 0-I), not melphalan exposure itself. So the causal chain from exposure to chronic GVHD runs through acute GVHD and could equally be read as a statement about acute GVHD severity. The mucositis-initiates-alloreactivity mechanism is the authors' prior hypothesis, and mucositis itself was not measured as a mediator. Dvorak CC et al. 2025
  3. E3strong confidence 4 of 5: Replicated in peer-reviewed work by more than one group.paper

    In JPLSG MLL-10, 38 of 43 first-remission transplants in high-risk KMT2A-rearranged infants used protocol-specified conditioning of individualised targeted busulfan, etoposide and cyclophosphamide, giving 3-year event-free survival of 56.8% (95% CI 42.4-68.8) and overall survival of 80.2% (95% CI 67.1-88.5).

    Hematopoietic stem cell transplantation for infants with high-risk KMT2A gene-rearranged acute lymphoblastic leukemia · Takachi T, Watanabe T, Miyamura T, Moriya Saito A, Deguchi T, Hori T, Yamada T, Ohmori S, et al. · Blood Advances 2021
    PMID 34500465DOI
    What this evidence cannot show

    Single-arm; the 56.8% EFS is in a high-risk stratum defined differently from Interfant-06's (KMT2A-r plus age under 180 days OR central nervous system leukaemia, rather than plus WBC at or above 300 x10^9/L), so the two protocols' high-risk groups are not the same population and their outcomes are not directly comparable. Attributing any part of the result to etoposide rather than to the targeted busulfan, the MRD-driven timing or the different denominator is not supported by the design.

    Evidence that argues against this (1)
    • The authors themselves decline to read their result as an endorsement of transplant with this or any conditioning: 'considering the high rate of potentially life-threatening toxicities and the risk of late effects, its indication should be further restricted or even eliminated in the future by introducing more effective therapeutic modalities with minimal toxicities.' A favourable conditioning outcome is being reported alongside a recommendation to use it less. Takachi T et al. 2021
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