ThioTEPA is an organophosphorus compound with the formula SP(NC₂H₄)₃.^[1] It is an analogue of N,N',N''- triethylenephosphoramide (TEPA). This molecule features tetrahedral phosphorus and is structurally akin to phosphate. It is derived from aziridine and thiophosphoryl chloride.

History and use

ThioTEPA was first developed by American Cyanamid company in the early 1950s and was reported in 1953.^[2] ThioTEPA has been in use since the 1960s.

ThioTEPA has been designated as orphan drug by the European Medicines Agency on January 29, 2007, and by the United States Food and Drug Administration (FDA) on April 2, 2007, as a conditioning treatment prior to haematopoietic stem cell transplantation.^[3] The applicant for these orphan drug designations was the Italian company ADIENNE Pharma & Biotech, owner of the drug TEPADINA (INN: thiotepa).

Thiotepa is indicated, in combination with other chemotherapy medicinal products:

• with or without total body irradiation (TBI), as conditioning treatment prior to allogeneic or autologous haematopoietic progenitor cell transplantation (HPCT) in haematological diseases in adult and paediatric patients;
• when high dose chemotherapy with HPCT support is appropriate for the treatment of solid tumours in adult and paediatric patients.^[4]

Thiotepa has been previously used in the palliation of a wide variety of neoplastic diseases. The more consistent results have been seen in: adenocarcinoma of the breast, adenocarcinoma of the ovary, superficial papillary carcinoma of the urinary bladder and for controlling intracavitary effusions secondary to diffuse or localized neoplastic diseases of various serosal cavities.^[4]

Thiotepa is also used as intravesical chemotherapy in bladder cancer. Three patterns of usage is identified. 1) prophylactic - before taking cystoscopic biopsy, to prevent seeding of tumor cells; 2) adjunctive- at the time of biopsy; 3) theraputic - to prevent recurrence after cystoscopic resection of bladder tumor (transurethral resection of bladder tumor - TURBT)

For theraputic usage, thiotepa is given in 30 mg doses intravesically weekly for 4–6 weeks. Many studies have reported up to 55% of success rate. Main toxicity of intravesical therapy is due to systemic absorption causing myelosupression, which results in thrombocytopenia and leukopenia.

Thiotepa main toxicity is myelosuppression. The most serious complication of excessive therapy is bone marrow depression, causing leukopenia, thrombocytopenia, and anemia.^[5] Serious toxicity involving the hematologic, hepatic and respiratory system were considered as expected consequences of the conditioning regimen and transplant process.