Roche's investigational haemophilia drug emicizumab cut the bleed rate by 87 percent in patients with resistance to standard therapy compared with those who received another treatment, the Swiss company said on Monday.

Roche is counting on emicizumab to wrest a share of the $11 billion-a-year haemophilia drug market now dominated by traditional treatments from Novo Nordisk and Shire.

Nearly 63 percent of patients receiving emicizumab experienced zero treated bleeds, compared with 5.6 percent of those getting so-called bypassing agents, according to data released ahead of the International Society on Thrombosis and Haemostasis (ISTH) industry meeting in Berlin in July.

Some analysts called Monday's data release convincing, with Jefferies saying it underpinned its $5 billion peak sales estimate for the medicine.

"If full presentation of the data at the ISTH reassures on safety, our mid-term EPS estimates and valuation could increase by 2 percent to 4 percent," Jefferies' Jeffrey Holford wrote in a note to investors.

Haemophilia patients' blood does not clot properly, requiring life-saving infusions of clotting factors.

Development of resistance, or inhibitors, in some patients can interfere with efforts to control bleeding, so Roche is hoping its drug, also known as ACE910, will offer a new avenue of treatment.

Still, analysts continue to cite adverse events in Roche's studies including thrombotic microangiopathy -- damage to blood vessels in vital organs -- that accompanied repeated high doses of bypassing agents given to counter bleeds that occurred despite emicizumab treatment.

Although Roche has played down emicizumab's role in the complications -- one death came after a patient refused a blood transfusion for religious reasons, it has said -- analysts' concerns linger.

Roche shares rose 0.4 percent by 0930 GMT, while the Stoxx European health care sector index firmed 0.1 percent.

SAFETY PERSPECTIVE

"From a safety perspective, treatment with this drug will require physicians to carefully manage the use of bypassing agents," Bank Vontobel's Stefan Schneider wrote. That "could limit uptake", he said.

Roche plans to file emicizumab with the US Food and Drug Administration this year for approval for patients with inhibitors, with follow-on submissions in 2018 including for patients without resistance.

Deutsche Bank analysts said Monday's data suggested it would be tough for emicizumab to make headway among those patients, however, since clotting factors appeared to be more effective for them.

"Current therapy in the non-inhibitor setting provides a very high hurdle to new entrants and we believe emicizumab's less than perfect efficacy and observed thrombotic events will temper enthusiasm for the drug," Deutsche Bank's Tim Race said.