Oncofusion

start / graph / drug-pegaspargase

Drugstrong confidence 4 of 5: Replicated in peer-reviewed work by more than one group.Q51-backbone

Pegaspargase - the same enzyme wearing a polymer, dosed in units that are not the other product's units, and now dosed to a level in every group except infants

also called pegaspargase · PEG-ASP · PEG-asparaginase · PEGasparaginase · Oncaspar · pegylated E. coli L-asparaginase · PEG-L-asparaginase

Pegaspargase is the same bacterial enzyme as plain asparaginase with a polymer coat that makes it last far longer, so one dose replaces many. It is a different product with different dosing numbers, and older children are now dosed by blood-level monitoring while infants are not.

The same thing, for a scientist

Pegaspargase is *E. coli* L-asparaginase covalently modified with monomethoxypolyethylene glycol, which extends the half-life and reduces immunogenicity. In Interfant-06 it is **2,500 U/m2 (Oncaspar)** IV over 1 hour or IM on **MARMA part II day 23** and **OCTADA(D) part I day 1** [E1] - two doses, against the six doses of native product in induction [see `drug-asparaginase`]. **The two are not interchangeable arithmetic:** the protocol cites COALL data that a single **45,000 U/m2** native dose gives asparagine and glutamine depletion of equal duration to one **2,500 U/m2** pegaspargase dose, an 18-fold unit ratio [E1], and it prescribes a **different substitution schedule** (5,000 U/m2 every 3 days x 9) when pegaspargase is unavailable. **The state of the art has moved and infants have not moved with it.** In DCOG ALL11, pegaspargase dosing was individualised against trough asparaginase activity levels of 100-250 IU/L using a population-PK-based guideline, raising the proportion in target after the first individualised dose from 13% to 32% and halving the number of dose reductions needed [E2]. Interfant-06 gives a fixed 2,500 U/m2 multiplied by 2/3 or 3/4 for age [E1]. **The KMT2A-specific evidence is the same as for the native product and belongs there:** 12-fold in-vitro resistance in infant and proB ALL [E3].

Go deeper
Why this is a separate entry, and what goes wrong when it is not

Pegaspargase and native E. coli asparaginase are the same catalytic enzyme and different drug products: different half-life, different immunogenicity, different dose in units, different schedule, different phases of this protocol. The trap is the same one this beat found in drug-prednisone versus drug-prednisolone - one word in the literature, two products in the patient - with an extra hazard, because here the units look comparable and are not.

native E. coli (Interfant induction)pegaspargase (Interfant MARMA/OCTADA(D))
dose10,000 U/m22,500 U/m2
doses in Interfant-066 (days 15, 18, 22, 25, 29, 33)2 (MARMA II day 23; OCTADA(D) I day 1)
protocol-cited equal-depletion dose45,000 U/m22,500 U/m2
substitution when unavailable-5,000 U/m2 every 3 days x 9

A unit count summed across a protocol is therefore not an asparaginase exposure, and 'total asparaginase units' is not a quantity this graph should ever compute. Any claim about asparaginase exposure in this disease must name the product.

A third enzyme sits behind the same word: Erwinia chrysanthemi asparaginase (crisantaspase/Erwinase), 20,000 U/m2 three times weekly, used after anaphylaxis 1. It is a different protein from a different organism, not a formulation of this one.

Level-guided dosing exists, and stops at the age floor

The Dutch Childhood Oncology Group ALL11 protocol individualised pegaspargase dosing against trough asparaginase activity of 100-250 IU/L after three fixed induction doses of 1,500 IU/m2. A refined population-PK-based guideline raised the proportion of patients within target after the first individualised dose from 13% to 32% (P < 0.001), cut the median number of dose reductions in medium-risk patients from 5 to 3 (P < 0.001), achieved >99% adherence, and reduced grade >=3 ALT elevation from 64% to 34% 2.

This is the same instrument drug-vincristine shows is missing. For two drugs in this backbone - vincristine and pegaspargase - therapeutic drug monitoring has been shown feasible, effective and well tolerated in paediatric practice, and Interfant-06 uses a fixed dose multiplied by an unjustified age factor for both. For a third - high-dose methotrexate - the protocol does monitor levels, but only to terminate rescue, never to assess exposure [see drug-methotrexate].

Why it matters most here. Silent inactivation by neutralising antibody is a documented and invisible failure mode of this drug class: the patient receives the dose, the enzyme is neutralised, and nothing signals it except an activity level. An infant receiving two pegaspargase doses at two-thirds of a fixed dose, with no activity level, has no mechanism by which that failure would be detected.

Facts and figures
targetcirculating L-asparagine (and L-glutamine), hydrolysed extracellularly; same catalytic activity as native E. coli asparaginase. Resistance gene of record for the class is ASNS; no ASNS node exists in this graph as of cycle 28.
modalitybacterial enzyme (biologic), E. coli L-asparaginase conjugated to monomethoxypolyethylene glycol
interfant06 positionMARMA part II day 23 and OCTADA(D) part I day 1 - two doses
interfant06 dose2,500 U/m2
infant dose adjustmentx 2/3 under 6 months, x 3/4 from 6 through 12 months; no activity-level monitoring in this protocol
unit equivalence warningThe protocol cites a COALL equivalence of one 45,000 U/m2 native E. coli dose to one 2,500 U/m2 pegaspargase dose for duration of asparagine and glutamine depletion - an 18-fold unit ratio. Summing 'asparaginase units' across a protocol is meaningless. Always name the product.
state of the art not applied to infantstrough asparaginase activity target 100-250 IU/L with population-PK-guided individualised dosing (DCOG ALL11); target attainment after the first individualised dose 32% vs 13%; >99% adherence; grade >=3 ALT elevation 34% vs 64%. No infants.
kmt2a specific evidenceINHERITED FROM THE NATIVE PRODUCT. The 12-fold in-vitro resistance of infant and proB ALL was measured with native L-asparaginase; pegylation alters pharmacokinetics rather than catalysis, so transfer is an inference. No pegaspargase-specific measurement in KMT2A-rearranged cells was found.
three products one word
[
  "native E. coli asparaginase (drug-asparaginase)",
  "pegaspargase, this entry",
  "Erwinia chrysanthemi asparaginase / crisantaspase / Erwinase - a DIFFERENT protein from a DIFFERENT organism, 20,000 U/m2 three times weekly after anaphylaxis"
]
key ae
[
  "hypersensitivity (lower than with the native product)",
  "silent inactivation by neutralising antibody - invisible without an activity level",
  "pancreatitis",
  "thrombosis and haemorrhage",
  "hepatotoxicity and transaminase elevation",
  "hypertriglyceridaemia",
  "hyperglycaemia"
]
resistance
[
  "asparagine synthetase expression (class mechanism; unmeasured in KMT2A-rearranged infant ALL)",
  "asparagine supplied in trans by bone-marrow mesenchymal cells",
  "anti-PEG and anti-asparaginase antibodies causing silent inactivation",
  "the proB immunophenotype, carrying 12-fold in-vitro resistance at any age"
]
trials
[
  "NCT00550992",
  "NCT02553460"
]
How this could bite us back
  • **An infant receives two doses of this drug, at two-thirds of a fixed prescription, with no way of knowing whether the enzyme is working.** Silent inactivation is a documented failure mode that produces no symptom and no laboratory abnormality other than the activity level nobody measures in this age group.
  • The obvious fix - import trough-activity-guided dosing into infant protocols - carries an unvalidated surrogate with it. Nobody has shown that a trough of 100-250 IU/L improves survival, so monitoring would deliver dose changes made against a target that is itself an assumption.
  • Allergy to the native product forces a switch to Erwinia asparaginase, a different protein with a shorter half-life and a supply history of international shortages. A strategy that raises hypersensitivity rates in infants raises demand for the one asparaginase that has repeatedly been unavailable.
  • This graph should not compute asparaginase exposure. Interfant-06 gives 60,000 U/m2 of native enzyme and 5,000 U/m2 of pegaspargase, and by the protocol's own cited equivalence the second is worth 90,000 U/m2 of the first. Adding them gives a number with no referent.
  • Two pegaspargase doses in a two-year protocol is a thin exposure for a drug considered among the most important in paediatric ALL, in the disease most resistant to it. Whether that is under-treatment or appropriate restraint is unanswerable without the activity measurements this population does not get.
Still open
  1. What trough asparaginase activity does an infant achieve after 2,500 U/m2 multiplied by 2/3? The assay exists, the target range exists, the guideline exists, and the age group with the largest in-vitro resistance is the one it has not been applied to.
  2. How often is pegaspargase silently inactivated in infants? Silent inactivation is invisible without an activity level, and no infant protocol in this graph measures one, so the failure rate of this drug in this population is structurally unknown.
  3. Does pegylation alter anything relevant besides pharmacokinetics in a proB blast? The assumption that the 12-fold resistance transfers rests on catalysis being unchanged, which is reasonable and untested in these cells.
  4. Three products, one word, an 18-fold unit ratio and a different organism behind the third. How many claims in this graph and in the wider literature about 'asparaginase exposure' are summing incommensurable units?
Every source behind this entry (4)
  1. E1established confidence 5 of 5: Multiple independent lines of evidence; treated as settled in the field.paper

    Interfant-06 gives pegaspargase (Oncaspar) 2,500 U/m2 IV over 1 hour or IM on MARMA part II day 23 and on OCTADA(D) part I day 1; if pegaspargase is unavailable, native E. coli asparaginase 5,000 U/m2 every 3 days for 9 doses is substituted, the protocol citing COALL data that one 45,000 U/m2 dose of native E. coli asparaginase gives asparagine and glutamine depletion of equal duration to one pegaspargase dose; after severe anaphylaxis to native E. coli asparaginase, pegaspargase 2,500 U/m2 every 2 weeks or Erwinase 20,000 U/m2 three times weekly is substituted.

    What this evidence cannot show

    A trial protocol document, not a peer-reviewed publication, and specifically the SKION (Dutch) national version of April 2006; the trial was amended during its course (asparaginase provisions in MARMA and OCTADA(D) among others), so later versions may differ. Doses given are PLANNED doses; delivered cumulative dose per patient is lower wherever a course was omitted, delayed or curtailed by a stopping rule, and the trial report does not publish delivered dose per patient. Retrieved and text-extracted by this beat on 2026-09-20 (90 pages, 194,979 characters); page numbers are the PDF's own. Asparaginase provisions are explicitly among the parts of Interfant-06 that were amended during the trial, so the schedule here is the April 2006 SKION version and a given patient's exposure may differ. The 45,000 U/m2 equivalence is attributed to COALL without a citation and was not verified against a primary source by this beat.

    Evidence that argues against this (1)
    • Equal duration of asparagine depletion is the field's surrogate for equal effect and is not equal effect. The move to trough-activity-guided dosing in contemporary protocols is itself evidence that fixed-unit prescriptions do not deliver equivalent exposure even within one product. Brigitha LJ et al. 2025
  2. E2strong confidence 4 of 5: Replicated in peer-reviewed work by more than one group.paper

    In DCOG ALL11, pegaspargase dosing was individualised after three induction doses of 1,500 IU/m2 to target trough asparaginase activity of 100-250 IU/L; a refined population-pharmacokinetic model-based guideline (92 patients, 714 samples) increased the proportion within target after the first individualised dose from 13% (47/354) to 32% (22/67) against the previous pragmatic guideline (P < 0.001), reduced the median number of dose reductions needed in medium-risk patients from 5 to 3 (P < 0.001), achieved adherence above 99% with 6 of 714 recommended doses deviating, and was associated with a lower proportion of patients with grade 3 or higher ALT elevation (34% vs 64%, P < 0.05) with otherwise comparable toxicity.

    PMID 39137448DOI
    What this evidence cannot show

    A before-and-after comparison of two dosing guidelines within one national protocol, not a randomised trial, so the toxicity difference is confounded by period. 92 patients in the new group. Standard-risk and medium-risk ALL patients on ALL11 - **no infants**, and the induction dose there is 1,500 IU/m2, not Interfant's 2,500. Cited to establish that level-guided dosing is feasible and improves target attainment, not to specify an infant regimen.

    Evidence that argues against this (1)
    • Target attainment is not an outcome. 32% in target after the first individualised dose is a large relative improvement and still means two-thirds of patients out of target, and no trial has shown that hitting a trough activity window of 100-250 IU/L improves event-free survival. Extending this apparatus to infants would import an unvalidated surrogate along with the monitoring. Orgel E et al. 2026
  3. E3strong confidence 4 of 5: Replicated in peer-reviewed work by more than one group.paper

    In the MTT assay, 44 infants with ALL were 12-fold more resistant to L-asparaginase than 425 children over 1 year with common/preB ALL (P = 0.001), and proB ALL of all ages showed the same relative resistance, with age not related to resistance within the proB or MLL-rearranged groups.

    In vitro drug-resistance profile in infant acute lymphoblastic leukemia in relation to age, MLL rearrangements and immunophenotype. · Ramakers-van Woerden NL, Beverloo HB, Veerman AJ, Camitta BM, Loonen AH, van Wering ER, et al. · Leukemia 2004
    PMID 14712291DOI
    What this evidence cannot show

    The product assayed was L-asparaginase, i.e. the native enzyme, not pegaspargase - the pegylation changes pharmacokinetics and immunogenicity, not catalysis, so the cellular sensitivity should transfer, but that is an inference and not a measurement. An MTT LC50 for an enzyme that depletes a medium nutrient measures sensitivity to asparagine withdrawal in a defined medium.

    Evidence that argues against this (1)
    • Because pegylation alters exposure rather than catalysis, the clinically relevant question for pegaspargase is whether adequate depletion is achieved and sustained in an infant - a pharmacokinetic question the in-vitro resistance measurement cannot address, and one that trough-activity monitoring answers directly and has never been applied in this age group. Brigitha LJ et al. 2025
  4. E4strong confidence 4 of 5: Replicated in peer-reviewed work by more than one group.paper

    A contemporary multicentre phase 1/2 infant ALL study used pegaspargase 2,500 units/m2 IV on day 5 of induction and days 3 and 8 of reinduction in 50 infants (median age 171 days, 35 KMT2A-rearranged) on a dexamethasone and mitoxantrone backbone with bortezomib and vorinostat, with hypertriglyceridaemia the most frequent grade 3-4 reinduction adverse event at 23% and all four treatment-related deaths infectious.

    PMID 41692013DOI
    What this evidence cannot show

    Single-arm, n = 50, primary endpoint tolerability, and the backbone contains two investigational agents so nothing can be attributed to pegaspargase specifically. The pegaspargase schedule here (three doses, in induction and reinduction) differs from Interfant-06's (two doses, in MARMA and OCTADA(D)), so this is a different exposure in the same age group.

    Evidence that argues against this (1)
    • Hypertriglyceridaemia is a characteristic asparaginase effect and the report does not attribute it, so its 23% frequency is suggestive rather than evidential. Conversely, the absence of reported pancreatitis or thrombosis among the frequent events does not establish that they did not occur, since the reporting threshold was 20% for induction events. Orgel E et al. 2026
Connected to