Tesaro jumps on PARP ovarian cancer data, as drug hailed a ‘breakthrough’

Tesaro ($TSRO) shares went flying after the company posted top-line data on its PARP inhibitor niraparib earlier this year--and for good reason. The drug showed it could hold off ovarian cancer, a disease with few treatment options.

Investors and pharma watchers have been salivating for details from that trial, and over the weekend, their appetites were satisfied. Niraparib delivered a median progression-free survival advantage of 15.5 months for patients with the BRCA mutation whose cancer had returned after previous treatment. That’s the population most likely to benefit from the PARP class of meds.

But niraparib did more than that; it also delayed cancer’s advance in patients who tested negative for a BRCA mutation. And even those thought least likely to benefit from the drug--patients without the mutation who also tested negative to another diagnostic, Myriad Genetics’ HRD--experienced a 3.1-month benefit.

That result could potentially lead to a broad FDA approval across ovarian cancer--an edge over AstraZeneca’s ($AZN) Lynparza, the only PARP inhibitor already on the market. The AZ drug has an FDA nod for BRCA-positive patients, about 10% to 15% of the ovarian cancer population.

Tesaro’s 553-patient trial included 203 who carried the BRCA mutation. BRCA patients in the niraparib arm lived a median 21 months without their disease progressing, compared with 5.5 months for patients in the placebo arm. Among patients without the BRCA mutation, progression-free survival was 9.3 months in the niraparib group, versus 3.9 months in the placebo group.

A smaller group of patients without the mutation saw better results: In those who tested positive for homologous recombination DNA repair deficiencies (HRD), niraparib delayed cancer’s advance by 12.9 months, compared with 3.8 months in the control group--an improvement of more than 9 months.

The study’s lead author, Dr. Mansoor Raza Mirza of Copenhagen University, called the data “a breakthrough” for ovarian cancer patients whose cancer has come back after treatment.

"We have never seen such large benefits in progression-free survival in recurrent ovarian cancer,” Mirza said in a statement. “Niraparib significantly improved all endpoints across a broad patient population representing 70% of all ovarian cancer patients. These landmark results could change the way we treat this disease.”

The impressive results are sure to raise hopes for other PARP inhibitors working their way up the pipeline, including talazoparib, a late-stage drug Pfizer ($PFE) will acquire in its $14 billion deal for Medivation ($MDVN).

The California biotech’s CEO, David Hung, has trumpeted Medivation’s talazoparib as a “best-in-class” PARP player, a mantra that got plenty of airtime while Big Pharmas including Sanofi ($SNY), Amgen ($AMGN), Novartis ($NVS), AstraZeneca and others were reportedly weighing bids.

And then there’s AstraZeneca’s Lynparza, which will be under the gun if Tesaro’s newest data help niraparib win a far-reaching label. Lynparza, with peak sales estimates of $2 billion, is one of the drugs CEO Pascal Soriot is counting on for growth--particularly in light of some recent clinical trial failures, including last week’s disappointment for the blood thinner Brilinta.

After falling short in a trial in patients with peripheral artery disease, AstraZeneca said its 2023 forecast of $3.5 billion in sales is now unrealistic.

The biotech’s shares were up around 18% by 10am ET this morning with a market cap of $6 billion.