(Reuters) - Tesaro Inc's experimental drug for treating chemotherapy-induced nausea and vomiting (CINV) failed to show enough benefit in trials to give it an edge over competing drugs, sending its shares down as much as 24 percent.
Merck & Co Inc's Emend, a drug similar to Tesaro's rolapitant, is approved to treat CINV and can help prevent it for up to 5 days from when chemotherapy is given.
Two late-stage trials showed that while rolapitant was effective in treating CINV during the 24-120 hour period following chemotherapy, it failed to significantly improve patients' condition during the first 24 hours.
Rolapitant also did not show significant improvement after 120 hours of initiating chemotherapy.
Rolapitant and Emend belong to the same class of drugs known as NK-1 receptor antagonists. These drugs work by blocking a substance in the brain that stimulates vomiting reflex.
Patients in the trials either received a combination of two drugs to reduce the side effects of chemotherapy or rolapitant plus the two-drug combo. Merck's drug is also used with the two-drug combination.
The most frequently observed adverse events, including fatigue, alopecia and loss of appetite, were balanced across both the patient groups, Tesaro said in a statement.
Tesaro said it continued to enroll patients in a third late-stage trial of the drug, and was preparing for a marketing approval application by mid-2014.
Over 70 percent of cancer patients undergoing chemotherapy suffer from nausea and vomiting that may result in a delay or discontinuation of treatment. Prolonged nausea and vomiting can also lead to weight loss, dehydration and malnutrition.
Tesaro acquired the development and marketing rights to rolapitant from Opko Health Inc in December 2010 for up to $121 million, including up-front and milestone payments.
Tesaro shares were down 20 percent at $30.11 in early trading on the Nasdaq.
(Reporting by Esha Dey in Bangalore, Additional reporting by Natalie Grover; Editing by Saumyadeb Chakrabarty)