(Reuters) – Patients taking a kidney cancer drug being developed by Aveo Pharmaceuticals Inc were half as likely to need a break from the medication due to side effects than those on the widely used medicine Nexavar, according to data released on Wednesday.

There were also significantly fewer patients taking Aveo’s tivozanib who required a dose reduction than those on Nexavar.

Aveo, which is developing tivozanib along with Japan’s Astellas Pharma, had already released preliminary data from the pivotal study showing that its drug delayed worsening of the disease longer than Nexavar, sold by Bayer AG and Onyx Pharmaceuticals.

The latest data, to be presented at next month’s American Society of Clinical Oncology (ASCO) meeting in Chicago, focused on safety and tolerability of the Aveo drug. It is being positioned as a potential front line, or initial treatment, for kidney cancer.

“The attractive feature for tivozanib is both the efficacy and the safety profile,” Dr Robert Motzer, the study’s lead investigator and an attending physician at Memorial Sloan-Kettering Cancer Center, said in a telephone interview.

Aveo plans to file its application seeking U.S. and European approval for tivozanib to treat renal cell carcinoma later this year. JP Morgan analysts have predicted 2013 approval and forecast annual sales reaching $590 million by 2015.

Due to toxicities associated with kidney cancer treatments, patients often require an interruption in the medication or a reduction in the dose.

In the 517-patient Phase III study, 18 percent of tivozanib patients needed dosing interruptions due to side effects, compared with 35 percent for Nexavar, also known as sorafenib.

The rate of patients requiring dose reductions was 14 percent for tivozanib compared with 44 percent for Nexavar. The results were deemed to be statistically significant, Aveo said.

Patients taking tivozanib had slightly higher incidence of high blood pressure and fatigue, while those who received Nexavar in the study reported a higher incidence of diarrhea and hand-foot syndrome, an uncomfortable skin condition that resembles a sunburn.

Motzer noted that one of the most important features of Nexavar has been its safety compared with other widely used kidney cancer drugs, making the results for Aveo’s treatment all the more significant.

“It seems to have very few effects like skin toxicity or diarrhea or fatigue that we see frequently in day-to-day management of kidney cancer,” Motzer said.

In previously released data, tivozanib delayed worsening of the cancer, known as progression-free survival, or PFS, by an average of 11.9 months versus 9.1 months for Nexavar. PFS was the study’s primary goal.

When looking only at patients who had not received prior similar therapy for their cancer, tivozanib extended PFS by an average of 12.7 months.

“It does look to me to be a very promising new therapy,” Motzer said.

Fifty-three percent of the Nexavar patients required subsequent therapy compared with 17 percent of the tivozanib patients, the company said.

Overall survival data, which compares how long the treatments extended life, is not expected to be fully available until 2013, Aveo said.

(Reporting By Bill Berkrot in New York; Editing by Michele Gershberg and Matthew Lewis)