Raltitrexed

Evidence Level: L5

Predicted Indications: 10

Raltitrexed

Pharmacist Assessment Report

Raltitrexed: From Colorectal Cancer to Sclerosing Cholangitis

One-Sentence Summary

Raltitrexed is a thymidylate synthase inhibitor (antifolate) used as a cytotoxic chemotherapy, with the available pharmacology data describing its use in colorectal cancer and malignant mesothelioma. The TxGNN model predicts it may be effective for sclerosing cholangitis, with a very high model score. There are currently 0 clinical trials and 0 publications supporting this prediction, so it rests on model output alone.

Quick Overview

Item	Content
Original Indication	Colorectal cancer and malignant mesothelioma (from pharmacology data; the Australian registration entry has no indication text)
Predicted New Indication	Sclerosing cholangitis
TxGNN Prediction Score	0.9997
Evidence Level	L5
Australia Market Status	Listed on the PBS Schedule (1 of 1 items) – TGA (ARTG) registration status is not included in this data
Number of PBS Items	1 (valid: 1)
Recommended Decision	Hold

Why is This Prediction Reasonable?

Detailed mechanism of action data is not available in the data compiled for this report. Based on known pharmacology, raltitrexed is a thymidylate synthase (TYMS) inhibitor. It blocks DNA synthesis in rapidly dividing cells, which underpins its use in colorectal cancer and malignant mesothelioma.

The link to sclerosing cholangitis is weak. This is an immune-mediated, fibroinflammatory biliary disease, and no plausible connection to thymidylate synthase inhibition has been established. The high TxGNN score (0.9997, model rank 823) is a model-based prediction only.

Cytotoxic antimetabolites can cause hepatotoxicity and transaminase elevation, which is a concern in a cholestatic liver disease.

Other Predicted Indications (all L5, all Hold)

Rank	Predicted Indication	TxGNN Score	Comment
2	Myelodysplastic syndrome	0.9997	Conceptual rationale exists, as antimetabolites such as azacitidine and decitabine are used in MDS. However, marked myelosuppression is a major liability in patients with existing cytopenias.
3–7	Sickle cell disease variants (Hb D, Hb E, beta-thalassaemia, Hb C, HPFH)	0.9996	Identical scores come from the TxGNN model (deep learning) and may reflect similarities the model learned between related diseases, not biological evidence. Raltitrexed has no demonstrated fetal haemoglobin-inducing activity, and myelosuppression could worsen anaemia.
8	Unclassified myelodysplastic syndrome	0.9996	Likely inherited from the parent MDS node. Same myelosuppression concern.
9	Refractory cytopenia of childhood	0.9996	A cytotoxic antifolate would be expected to worsen marrow suppression. Paediatric safety data are lacking.
10	Partial deletion of the long arm of chromosome 5	0.9995	Related to del(5q) MDS, where lenalidomide acts via a distinct mechanism. No link to thymidylate synthase inhibition is established.

Clinical Trial Evidence

Currently no related clinical trials registered.

Literature Evidence

Currently no related literature available.

Australia Market Information

ARTG Number	Product Name	Dosage Form	Approved Indication
ARTG 4610P	Tomudex	Powder for I.V. infusion, 2 mg in single use vial	Not stated in the data compiled for this report

Cytotoxicity

Item	Content
Cytotoxicity Classification	Conventional cytotoxic (antifolate, thymidylate synthase inhibitor)
Myelosuppression Risk	High. Myelosuppression is a dose-limiting toxicity.
Emetogenicity Classification	Please refer to the Product Information (PI) warnings and precautions
Monitoring Items	FBC (with differential), liver function and renal function. Please also refer to the PI.
Handling Protection	Must follow cytotoxic drug handling regulations

Safety Considerations

Hepatotoxicity: Cytotoxic antimetabolite toxicity, including transaminase elevation, is a concern in cholestatic liver disease such as sclerosing cholangitis.
Myelosuppression: This is a major liability in patients with pre-existing cytopenias (MDS, refractory cytopenia of childhood) and in haemoglobinopathies, where antifolate-induced cytopenias could worsen anaemia.
Paediatric use: Paediatric safety data for raltitrexed are lacking.
Drug Interactions: The interaction query found only the pharmacological target, thymidylate synthase (TYMS). No drug-drug interactions were identified.

Warnings and contraindications from the label were not available. Please refer to the TGA-approved Product Information (PI) for full safety information.

Conclusion and Next Steps

Decision: Hold

Rationale: All predicted indications are supported by model output only (L5), with no registered trials or publications. There is no plausible mechanistic link for the top prediction, sclerosing cholangitis. The known toxicity profile (hepatotoxicity, marked myelosuppression) is a significant concern in the predicted conditions.

To proceed, the following is needed:

Product Information (PI) warnings and contraindications for the Australian-registered product (ARTG 4610P), which are required before any safety screening
Detailed mechanism of action data, to assess any mechanistic link
Preclinical or mechanistic studies to establish a biological rationale for the top-ranked indications
A review of why the TxGNN model (deep learning) produced identical scores across the sickle cell variants, to check whether the signal only reflects similarities the model learned between related diseases rather than biological evidence
A safety assessment specific to hepatic impairment, pre-existing cytopenias and paediatric populations
Disclaimer

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