Novartis, which forecasts Entresto will eventually hit $5 billion in annual sales, has seen its introduction last year get off to a slow start. In January, it called sales “quite below what we anticipated,” amid resistance from insurers, among other obstacles.

At the American College of Cardiology’s meeting in Chicago on Saturday, Novartis told doctors that clinically stable heart patients, as well as those considered least stable, both appear to benefit from taking Entresto compared to enalapril, a generic introduced 35 years ago that remains a standard heart failure treatment.

“Among both groups, patients taking Entresto had a 20% or greater reduction in cardiovascular death or heart failure hospitalization compared to those taking enalapril,” Novartis said in a statement, citing conclusions based on analysis of data from the PARADIGM-HF study.

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Novartis (NVS) shares have lost more than a fifth of their value this year, in part due to concerns about its lagging eyecare business Alcon as well as Entresto’s prospects for meeting ambitious expectations.

Last week, analysts at UBS cited Entresto uncertainty as a reason for their downgrade of Novartis shares to neutral, from buy.

“Novartis’ earnings momentum has been negative since the second quarter of 2015, triggered by deteriorating Alcon prospects, compounded by eroding expectations for blockbuster candidate Entresto, in view of its disappointing U.S. uptake,” wrote UBS’s Alexandra Hauber in a note.

“Our in-depth review of the ongoing U.S. clinical debate leaves us fairly confident Entresto can still turn into the $5 billion blockbuster predicted by Novartis, though significant acceleration of script trends may not materialise before mid-2017.”

Novartis said taking Entresto twice a day reduces strain on a failing heart.