Methotrexate

Evidence Level: L5

Predicted Indications: 7

Methotrexate

Pharmacist Assessment Report

Methotrexate: From Acute Lymphoblastic Leukemia to Pulmonary Blastoma

One-Sentence Summary

Methotrexate is an established antifolate drug, used for acute lymphoblastic leukemia, lymphomas, rheumatoid arthritis and psoriasis. The TxGNN model predicts it may be effective for pulmonary blastoma, a rare aggressive lung tumour. So far there are 0 clinical trials and 0 publications supporting this specific prediction, so it rests on the model score alone.

Quick Overview

Item	Content
Original Indication	Acute lymphoblastic leukemia (other listed uses include non-Hodgkin lymphoma, mycosis fungoides, rheumatoid arthritis and psoriasis)
Predicted New Indication	Pulmonary blastoma
TxGNN Prediction Score	0.9945
Evidence Level	L5
Canada Market Status	Marketed (marketed DINs on record: at least 19; cancelled: 1)
Number of DINs	at least 20
Recommended Decision	Hold

The Canadian licence records compiled for this report contain no indication text. The original indication is therefore not stated on this page.

Why is This Prediction Reasonable?

Methotrexate blocks the enzyme dihydrofolate reductase (DHFR) and so disrupts thymidylate and DNA synthesis in rapidly dividing cells. This is the basis of its use in leukemia and lymphoma, where fast-growing cells are especially vulnerable.

Pulmonary blastoma is an aggressive, embryonal-type lung tumour. Because it is fast-growing, a general antifolate rationale is plausible, and this is probably why the model links it to methotrexate.

This is a mechanism-based extrapolation only. The data compiled for this report contain no trials, case reports or other publications of methotrexate in pulmonary blastoma. The tumour is also very rare, which makes prospective evidence hard to generate.

Clinical Trial Evidence

Currently no related clinical trials registered.

Literature Evidence

Currently no related literature available.

Canada Market Information

The records compiled for this report do not include dosage form or approved-indication text. The first five are shown below.

DIN	Product Name
02099705	Methotrexate Sodium Injection
02454874	Metoject Subcutaneous
02491338	Methotrexate Subcutaneous
02454831	Metoject Subcutaneous
02454769	Metoject Subcutaneous

Other products include Methotrexate Tablets USP (02182750), PMS-Methotrexate Injection, Methofill Self-Dose Injector, Nordimet and ACH-Methotrexate.

Cytotoxicity

Item	Content
Cytotoxicity Classification	Conventional cytotoxic (antimetabolite, antifolate class)
Myelosuppression Risk	High, especially at high doses (leukopenia, thrombocytopenia and anemia are recognised)
Emetogenicity Classification	Low to moderate, dose-dependent
Monitoring Items	CBC with differential, liver and renal function, and methotrexate levels for high-dose regimens
Handling Protection	Must follow cytotoxic drug handling regulations

This is based on general drug-class knowledge, because the compiled data contain no detailed toxicity information. Please also refer to the package insert warnings and precautions.

Safety Considerations

Contraindication-type associations (from the TxGNN knowledge graph, not label text): The graph links methotrexate to the following conditions. They should be treated as caution signals until verified against the label:

Liver failure and liver disease
Kidney disease
Gallbladder disease
Thrombocytopenia, leukopenia and anemia (including macrocytic anemia)
Interstitial lung disease and pulmonary fibrosis
Peptic ulcer disease and gastric ulcer
Ulcerative colitis and inflammatory bowel disease
Stomatitis
Immune system disease
Substance abuse/dependence
Pyoureter

Drug Interactions: 100 interactions were identified in total. The main ones are:

Major: rabeprazole, amoxicillin, acetylsalicylic acid
Moderate: acarbose, doxycycline, tetracycline, clarithromycin, pioglitazone, bupropion, amphotericin B, mesalazine, balsalazide, and corticosteroids (hydrocortisone, dexamethasone, betamethasone, triamcinolone, budesonide)
Minor: potassium citrate

Please refer to the package insert for the full warnings and contraindications.

Conclusion and Next Steps

Decision: Hold

Rationale: The prediction score is very high (0.9945), but there are no trials or publications for pulmonary blastoma (Evidence Level L5). The only support is a generic antifolate mechanism. Methotrexate is marketed in Canada and its safety profile is well known, but this does not substitute for disease-specific evidence.

Other predictions for methotrexate have more support in the compiled data:

Hodgkin lymphoma and rhabdomyosarcoma are at L2.
Primary pulmonary lymphoma is at L4.

These may be better candidates to prioritise.

To proceed, the following is needed:

Disease-specific evidence for methotrexate in pulmonary blastoma, such as case series, preclinical models or tumour folate-pathway data
Detailed mechanism of action data (MOA)
Package insert warnings and contraindications from Health Canada
Review of how this rare tumour is currently treated, to judge whether methotrexate adds anything to existing options
A safety monitoring plan, including dose, route and organ-function considerations for lung-tumour patients
Disclaimer

This content is for research purposes only and does not constitute medical advice. Clinical validation is required before any clinical application.