Tesmilifene is a small molecule chemopotentiator under development by YM BioSciences, a Candian pharmaceutical company that specialises in the development of cancer treatments. It is indicated for use in combination with standard cytotoxic drugs, such as taxanes and anthracyclines, which are widely used in the treatment of metastatic disease – when cancers spread to distant sites in the body.

DRUG RESISTANCE LIMITS EFFECTIVENESS OF CHEMOTHERAPY

Cytotoxic drugs have proved potent weapons in the fight against malignant tumours and are considered first-line therapy for the treatment of many cancers. However, while patients often respond well to a first course of chemotherapy over time the response to drug treatment diminishes and the tumour may eventually become drug resistant. In some cases resistance can develop across several classes of anti-cancer drugs, leading to multidrug resistance. The development of drug resistance limits the effectiveness of many anti-cancer agents and is an important contributor to cancer deaths.

The development of agents that can overcome drug resistance is seen as one of the most important areas of cancer research and for which there is significant unmet need. Various approaches are being explored to boost the use of cytotoxic agents including chemopotentiators, chemoprotectants and liposomal formulations.

Clearly any agent that can prevent or reverse drug resistance would have a major impact on treatment strategies, enhancing the benefits of standard cytotoxic drugs.

TESMILIFENE MAY BOOST CYTOTOXIC EFFECTS OF ANTHRACYCLINES

Anthracyclines are a class of cytotoxic agents with proven efficacy in the treatment of breast cancer. They include agents such as doxorubicin and epirubicin among others. Because patients with metastatic breast cancer may have received anthracycline therapy for earlier stage breast cancer (adjuvant therapy) or following disease recurrence, there is a risk that they will fail to respond to continued treatment.

A phase III trial in 305 patients with advanced breast cancer has shown that when tesmilifene is combined with doxorubicin it appears to improve survival over treatment with doxorubicin alone. In this trial approximately half the patients were treated with both tesmilifene and doxorubicin, while the other half received doxorubicin alone.

Although there were no significant differences in tumour response rates, progression-free survival, or average duration of response between treatment arms at endpoint, overall survival was significantly improved in the combination arm. Among patients treated with tesmilifene and doxorubicin overall survival was 23.6 months compared with 15.6 months for those treated with doxorubicin alone.

Researchers have suggested that tesmilifene may enhance the anti-tumour effects of anthracyclines in several ways:

Reducing the cancer cell’s ability to become resistant;

Decreasing the metabolism or “break-down” of doxorubicin;

Disrupting the cancer cell’s energy source.