Sanofi has winning cancer drug, but short patent

A logo of pharmaceutical company Sanofi Aventis is seen in Ambares near Bordeaux, southwestern France, September 20, 2006.

LONDON (Reuters) - Sanofi-Aventis may have bagged a winning cancer drug when it agreed to buy privately held BiPar Sciences for up to $500 million in April, but a short patent could limit the French group's scope to cash in on sales.

BiPar's BSI-201 has emerged as one of the most promising new products at this year's ASCO cancer conference in Orlando, Florida, with positive mid-stage trial results helping lift Sanofi shares by more than 3 percent on Monday.

But there is a fly in the ointment. A Sanofi spokesman said on Monday that the main U.S. composition patent on the medicine was valid only until 2013, though this could be extended by five years.

In Europe, the patent runs to 2014 and Sanofi will have 10 years data exclusivity after approval.

"These facts probably explain the relatively modest agreed price for the BiPar deal," analysts at Morgan Stanley said in a research note.

They estimate BSI-201 could sell between $1 billion and $4 billion a year to Sanofi's 2016 revenues, with a U.S. launch as possible by late 2010.

On the face of it, that makes the price Sanofi's new chief executive, Chris Viehbacher, paid for BiPar seem a bargain. The problem is the medicine could face generic competition in the world's biggest pharmaceuticals market from 2018.

BSI-201 belongs to a new class of drugs that block a cell repair enzyme known as PARP.

It impressed doctors at the annual meeting of the American Society of Clinical Oncology (ASCO) on Sunday by improving survival by 60 percent compared with chemotherapy alone for women with tough-to-treat "triple negative breast cancer."

Patients with triple negative metastatic breast cancer have tumors that do not express the hormones oestrogen or progesterone, as well as the protein HER-2.

These women, who account for 15 to 20 percent of breast cancer patients, have a very aggressive form of disease and there are currently no treatments other than chemotherapy.

Citigroup analyst Mark Dainty said the data for BSI-201 was significantly better than the results with Roche's Avastin in triple negative patients and the new drug could put 20 to 25 percent of Avastin sales forecasts at risk.

Citi currently forecasts 2011 Avastin breast cancer sales at 1.7 billion Swiss francs ($1.6 billion) and losing 20 percent of this would slice some 2 percent off Roche's 2011 earnings per shares.

AstraZeneca also has an experimental PARP inhibitor called olaparib that is further behind in development.

For more on the new drug class, please click on

($1=1.063 Swiss Franc)

(Editing by Karen Foster)