Onconase is a new chemotherapy that is being tested for treatment for mesothelioma. Currently the popular drug used is Doxorubicin, however Onconase is beginning to increase in popularity as studies show that Onconase does not produce the debilitating side effects of Doxorubicin. Onconase works slowly, but is far less toxic than standard cancer drugs. There is none of the hair loss, anemia, or nausea normally associated with chemotherapy. Patients who react positively to Onconase live longer and have a higher quality of life.

Onconase is a ribonuclease protein derived from the eggs and embryonic stem cells of a species of leopard frogs. Onconase slows down cancer cell growth by decaying RNA. Without certain RNA strands cancer cells cannot make certain critical proteins and therefore cannot replicate. This slows down the growth of the tumor. Normally, high doses of chemotherapy are needed to affect cancer cells. However, Onconase is able to make cancer cells more susceptible to lower doses of chemotherapy, and therefore reduce side effects.

Onconase is the first ribonuclease protein drug, and one of the first embryonic stem cell products to reach the final stages of testing. Onconase seems effective on 90% of types of cancers. Because of its novelty its use in fighting mesothelioma is not well known. As published in the January 1, 2002 issue of the Journal of Clinical Oncology, clear anti-tumor activity was seen in 6 of the 81 patients and an additional 35 patients had cessation of growth in previously growing mesothelioma. The median survival of the patients who entered the trial without symptoms from the cancer was 18.5 months. In another study comparing patients using Onconase to those using Doxorubicin the median survival times, 1-year, and 2-year survival rates were 11.3 months vs 9.1 months, 46.2% vs 34.5%, and 34.3% vs 10.7%, respectively. The investigators concluded that Onconase is at least as active as Doxorubicin for the treatment of MM and may be more active in certain patient subsets.