Skip to content
Back to full profile

Antifolate (TS inhibitor)

Raltitrexed

Tomudex · Ralti

Antifolate (TS inhibitor) · approved 1996 · 4 references

A renally-cleared antifolate whose grandparent compound (CB3717) was withdrawn for crystal nephrotoxicity.

Signature injury
Acute Tubular Necrosis
Severity
Moderate
Reversibility
Partially reversible
Onset
Within the first one to two cycles, often heralded by exaggerated systemic toxicity in patients with reduced GFR.

Signature kidney injury & incidence

Acute Tubular Necrosis.

Not well quantified as a discrete renal endpoint. Raltitrexed is substantially renally eliminated: in a PK study, mild-to-moderate renal impairment roughly doubled drug exposure (AUC ratio ~2.0) and nearly doubled terminal half-life, with severe/grade 3-4 toxicity and adverse-event hospitalizations more frequent in the impaired group. The class precedent CB3717, raltitrexed's quinazoline antifolate forerunner, was withdrawn from development for crystal-related nephrotoxicity.

Source: Judson et al., Br J Cancer 1998 (AUC ratio ~2.0 in renal impairment)

Reported injury signatures: Acute Tubular Necrosis, Crystal / Obstructive Nephropathy.

Renal toxicity profile

  1. Acute Tubular NecrosisPrimary
  2. Crystal / Obstructive NephropathySecondary

Onset timing & rechallenge

Subacute (~1–6 weeks) — Within the first one to two cycles, exaggerated in patients with reduced GFR.

Mechanism of kidney injury

Two linked mechanisms. (1) Because the drug and its active polyglutamates are cleared substantially by the kidney, impaired renal function causes drug accumulation that amplifies systemic antifolate toxicity (myelosuppression, mucositis, hepatic and constitutional effects) and can secondarily worsen renal function through volume depletion and tubular stress. (2) By analogy to its quinazoline antifolate forerunner CB3717 (N10-propargyl-5,8-dideazafolic acid), which precipitated in the renal tubule and caused crystal nephropathy leading to its withdrawal, the structural class carries an intrinsic risk of intratubular crystal deposition and proximal tubular injury. Raltitrexed was engineered to be more water-soluble and less nephrotoxic than CB3717, so clinical crystal nephropathy is uncommon, but the accumulation-toxicity relationship in renal impairment is well documented.

Clinical presentation

Most commonly a creatinine rise in the setting of severe systemic antifolate toxicity (cytopenias, mucositis, diarrhea, transaminitis) when given to a patient with unrecognized renal impairment. Direct tubular/crystal injury would present as a subacute creatinine rise with bland-to-granular sediment; the precursor-class lesion was crystalline. Reduced thymidine-rescue effectiveness if AKI is severe.

Management

Hold for AKI or for exaggerated systemic toxicity; supportive care with hydration and management of cytopenias/mucositis. Folinic acid (leucovorin) rescue is used for overdose or severe toxicity. Re-dose only after renal recovery with appropriate reduction.

Risk factors

  • Pre-existing renal impairment (CrCl < 65 mL/min)
  • Volume depletion
  • Concurrent nephrotoxins
  • Failure to dose-reduce/extend interval for renal function

Prevention

  • Measure creatinine clearance before each cycle and dose-reduce or extend the interval for impaired GFR per the published renal banding (raltitrexed has no US label)
  • Avoid in severe renal impairment
  • Avoid concurrent nephrotoxins and folate-pathway interacting drugs

Renal dose adjustment

Dose by creatinine clearance: full dose for CrCl >= 65 mL/min; reduce dose and lengthen the dosing interval for CrCl 25-65 mL/min (e.g., reduced dose every 4 weeks); not recommended for CrCl < 25 mL/min. Always recalculate GFR before each cycle.

Dialyzability & ESKD dosing

Polyglutamated, tissue-retained antifolate cleared largely by the kidney; not characterized as efficiently dialyzable and not recommended in dialysis-dependent patients.

Differential diagnosis

Distinguish accumulation-driven systemic antifolate toxicity with secondary renal stress from intrinsic tubular/crystal injury; the precursor CB3717 lesion was crystalline. A patient presenting with severe pancytopenia/mucositis and a creatinine bump usually has under-recognized baseline renal impairment driving overexposure.

Monitoring

  • Complete blood count (nadir myelosuppression)
  • Liver function tests
  • Mucositis/diarrhea assessment

Key trials & series

  • Judson Br J Cancer 1998 renal-impairment pharmacokinetic study
  • Pivotal Tomudex colorectal-cancer registration program

Clinical pearls

  • Its forerunner CB3717 was abandoned for crystal nephrotoxicity; raltitrexed was redesigned to be more soluble, but the class still warrants renal caution.
  • Severe pancytopenia plus a creatinine rise after one cycle should prompt folinic-acid rescue and a hunt for unrecognized CKD.

Anticancer mechanism

Quinazoline folate-based, direct and specific inhibitor of thymidylate synthase (TS). After transport via the reduced-folate carrier it is polyglutamated intracellularly to highly potent, long-retained forms that block TS, depleting thymidine triphosphate and arresting DNA synthesis. Used mainly for advanced colorectal cancer (notably where fluoropyrimidines are not tolerated) and malignant mesothelioma.

Note

The actionable issue is renal clearance: impaired GFR sharply raises exposure and toxicity, so renal dosing is mandatory. Frank crystal nephropathy is a class-precedent (CB3717) risk rather than a common raltitrexed event; language here is deliberately conservative.

Guidelines & consensus

Each recommendation below is this atlas's faithful summary of the source, not a quotation from it — follow the PubMed link for the wording the society published. Summaries may be superseded; consult the current full text and individualize to the patient.

  • ADQI (2026) — Conventional cytotoxic chemotherapy-associated nephrotoxicity: consensus report of the 34th Acute Disease Quality Initiative (ADQI) WorkgroupCisplatin is identified as a leading cytotoxic nephrotoxin; the workgroup details preventive measures (adequate isotonic hydration, correction of volume depletion, avoidance of concurrent nephrotoxins, attention to electrolyte/magnesium wasting) and management of cisplatin-associated AKI, with a research agenda for knowledge gaps.Kidney Int · PMID 41881107
  • ADQI (2026) — The nephrotoxic effects of anti-cancer therapies: consensus report of the 34th Acute Disease Quality Initiative workgroupProvides expert-based statements (modified Delphi) on preventing and managing cisplatin/platinum-associated AKI, including isotonic IV hydration, attention to volume status and concomitant nephrotoxins, and incorporates evidence that IV magnesium supplementation may reduce cisplatin-associated AKI; emphasizes risk stratification and standardized AKI definitions.Nat Rev Nephrol · PMID 41361704
  • SIRM (2022) — SIRM-SIN-AIOM: appropriateness criteria for evaluation and prevention of renal damage in the patient undergoing contrast medium examinations-consensus statements from Italian College of Radiology (SIRM), Italian College of Nephrology (SIN) and Italian Association of Medical Oncology (AIOM)Recommends eGFR-based renal risk assessment and pre/post-contrast isotonic saline or sodium bicarbonate hydration; advises maintaining a 5-7 day interval between iodinated contrast administration and cisplatin in cancer patients to reduce additive nephrotoxicity.Radiol Med · PMID 35303246
  • KDIGO (2020) — KDIGO Controversies Conference on onco-nephrology: understanding kidney impairment and solid-organ malignancies, and managing kidney cancerIdentifies platinum compounds (especially cisplatin) as leading cytotoxic causes of acute tubular injury, AKI, and electrolyte/magnesium wasting; calls for interdisciplinary onco-nephrology care, accurate GFR estimation, and individualized drug dosing in patients with reduced kidney function.Kidney Int · PMID 33126977
  • KDIGO (2020) — KDIGO Controversies Conference on onco-nephrology: kidney disease in hematological malignancies and the burden of cancer after kidney transplantationAddresses chemotherapy-associated AKI/CKD in hematologic cancer, GFR estimation and chemotherapy dosing in patients with reduced kidney function, and management priorities and research gaps for onco-nephrology care.Kidney Int · PMID 33276867
  • ADDIKD (2025) — Integrating International Consensus Guidelines for Anticancer Drug Dosing in Kidney Dysfunction (ADDIKD) into everyday practiceProvides GRADE-based, drug-specific dose-adjustment recommendations for anticancer agents in kidney dysfunction (illustrated for methotrexate, cisplatin, carboplatin and nivolumab); the recommendations build on Part 1's standardised CKD-EPI eGFR assessment rather than Cockcroft-Gault creatinine clearance.EClinicalMedicine · PMID 40290844
  • ADDIKD (2025) — Aligning kidney function assessment in patients with cancer to global practices in internal medicineThree consensus recommendations: assess kidney function by GFR (measured GFR or CKD-EPI eGFR), classify it using KDIGO categories, and use this uniform approach to dose anticancer drugs — moving cancer medicine away from Cockcroft-Gault estimated creatinine clearance.EClinicalMedicine · PMID 40290845
  • ADDIKD (2025) — A methodology for determining dosing recommendations for anticancer drugs in patients with reduced kidney functionEstablishes that, where RCT evidence is lacking, anticancer drug dosing recommendations in kidney dysfunction should be derived by critically appraising observational literature via GRADE combined with structured international multidisciplinary consensus voting.EClinicalMedicine · PMID 40290846
  • KDIGO (2013) — Diagnosis, evaluation, and management of acute kidney injury: a KDIGO summary (Part 1)Defines/stages AKI by serum creatinine and urine output; emphasizes avoiding nephrotoxins, maintaining euvolemia/perfusion, dose-adjusting drugs to kidney function, and monitoring high-risk patients — the framework applied to nephrotoxic anti-cancer agents.Crit Care · PMID 23394211
  • KDIGO (2024) — Executive summary of the KDIGO 2024 Clinical Practice Guideline for the Evaluation and Management of Chronic Kidney Disease: known knowns and known unknownsEvaluate and risk-stratify CKD, manage to delay progression and its complications, and practise explicit medication management and drug stewardship — the framework the atlas's G1–G5 eGFR banding and every renal dose-adjustment recommendation sit inside. Because the guideline excludes dialysis and transplant recipients by its own statement of scope, its recommendations do not carry to those settings, where this atlas's dialyzability and post-transplant guidance rests on other sources.Kidney Int · PMID 38519239
  • KDIGO (2021) — Executive summary of the KDIGO 2021 Guideline for the Management of Glomerular DiseasesProvides the staging/treatment framework for drug-associated glomerular lesions (e.g., bisphosphonate- and interferon-related collapsing FSGS, VEGF-inhibitor podocytopathy/proteinuria), including immunosuppression and supportive RAAS-blockade strategies.Kidney Int · PMID 34556300
  • KDIGO (2024) — Executive summary of the KDIGO 2024 Clinical Practice Guideline for the Management of ANCA-Associated VasculitisUpdates immunosuppressive induction (rituximab/cyclophosphamide), incorporates avacopan and lower-dose or glucocorticoid-sparing regimens — the management framework for drug- and checkpoint-inhibitor-associated ANCA/pauci-immune glomerulonephritis.Kidney Int · PMID 38388147
  • KDIGO (2024) — Executive summary of the KDIGO 2024 Clinical Practice Guideline for the Management of Lupus NephritisUpdates first-line lupus nephritis therapy to combination immunosuppression with the addition of belimumab or a calcineurin inhibitor (voclosporin) — informs management of immune-complex/lupus-like glomerulonephritis encountered with immunotherapy.Kidney Int · PMID 38182299
  • KDIGO (2025) — Executive summary of the KDIGO 2025 Clinical Practice Guideline for the Management of Immunoglobulin A Nephropathy (IgAN) and Immunoglobulin A Vasculitis (IgAV)Encourages liberal kidney biopsy and stricter proteinuria control (<0.5 g/d, ideally <0.3 g/d) with RAAS blockers, SGLT2 inhibitors, and targeted-release budesonide — the framework for IgA-dominant glomerular lesions, including those triggered by immune-modulating cancer therapy.Kidney Int · PMID 40975525

References

4 peer-reviewed references. Citation metadata via PubMed / NLM.

  1. 1.Effects of impaired renal function on the pharmacokinetics of raltitrexed (Tomudex ZD1694).Judson I et al. · Br J Cancer · 1998 · PMID 9820178
  2. 2.Folate-based thymidylate synthase inhibitors as anticancer drugs.Jackman AL et al. · Ann Oncol · 1995 · PMID 8624289
  3. 3.Conventional Chemotherapy Nephrotoxicity.Gupta S et al. · Adv Chronic Kidney Dis · 2021 · PMID 35190107
  4. 4.Acute Kidney Injury in Patients with Cancer.Rosner MH et al. · N Engl J Med · 2017 · PMID 28467867
Educational monograph from NephTox (nephtox.com). Not medical advice — verify against current guidelines before any clinical decision.