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the two-drug chemotherapy regimen. Aside from any survival advantage, vosaroxin doesn’t appear to cause the heart toxicity associated with anthracyclines, Swisher says. And as far as researchers know, two common mechanisms that cancer cells use to become resistant to the effects of drugs won’t work against vosaroxin.
That said, a similar drug called amonafide that also showed promise in early clinical trials failed in a Phase III trial in 2011, sinking the prospects of UK-based drug developer Antisoma. Wall Street oddsmakers have been making bets that the Sunesis trial will also fail. They read the September decision to expand the trial population as a negative signal, according to TheStreet.com.
Swisher says the critics missed the hopeful signs in that pre-planned, interim review of the data so far.
“That bearish argument is not very informed in terms of really understanding the trial design,” Swisher says.
VALOR has an adaptive trial design that contemplated a one-time increase in enrollment to maintain the statistical power of the study, he says. The data and safety monitoring board’s evaluation, which placed the results in a pre-specified category defined as “promising,” triggered a $25 million payment to Sunesis by the life sciences investment firm Royalty Pharma, which gained royalty rights of 6.75 percent on future vosaroxin sales.
Sunesis has other avenues to pursue if its leading drug candidate falls short of the results needed for regulatory approval. The company could explore the use of vosaroxin in solid tumors such as ovarian cancer, as a frontline treatment for elderly AML patients who can’t withstand standard therapies, and as a therapy for myelodysplastic syndrome, a precursor of AML. Sunesis also has early stage clinical collaborations with Millennium/Takeda and Biogen Idec, which each include the possibility of milestone payments up to $60 million as well as product royalties. The company says its $61 million in cash will carry it past the announcement of the VALOR trial results in 2014, when it hopes to file for US and European regulatory approval for vosaroxin. If approved, the drug could be on the market in 2015.
Sunesis, which retains ownership of vosaroxin, estimates peak revenues at $700 million to $1.26 billion by 2020, assuming that the drug is used to treat about a quarter of the 49,000 relapsed and refractory AML patients in the United States and Europe. The US price for a treatment cycle would be $80,000 to $100,000.