It was a hotly anticipated pipeline drug. Now, Novartis' heart failure remedy Entresto is a hot new approval. The FDA gave its blessing 6 weeks early, and now the former LCZ696 can get ready to roll.

The approval comes after Entresto aced an 8,442-patient clinical trial against a common therapy, rather than placebo. At the end of the study, patients with a particular form of heart failure were more likely to be alive and less likely to have been hospitalized than the patients taking enalapril, the current standard of care.

The data were so positive, trial investigator Dr. Milton Packer has said he'd have a hard time understanding why doctors would continue using traditional treatments. "Entresto is expected to change the management of patients with HFrEF for years to come," Packer said in a statement about Tuesday's approval.

Novartis pharma chief David Epstein

Of the almost 6 million Americans with heart failure, about half have the reduced ejection fraction form that's targeted by Entresto, Novartis ($NVS) says. That means millions of potential patients for a drug Novartis pharma chief David Epstein has called its "most exciting launch" in years.

The drug's survival advantage--a 20% decrease in heart-related death, the trial found--coupled with a large patient population has analysts predicting megablockbuster sales. Some say as much as $10 billion a year--and consensus estimates put sales at $3.73 billion by 2019.

"[M]illions of people diagnosed with reduced ejection fraction heart failure now have a much greater opportunity to live longer and stay out of hospital," Epstein said in a statement. "We recognize our responsibility to ensure Entresto reaches US patients and prescribers as soon as possible and will begin shipping in the US in the coming week."