Doctors have long struggled to effectively treat heart failure caused by high blood pressure. ACE inhibitors, like enalapril -- formerly sold by Merck (NYSE:MRK) as the branded drug Vasotec, came on the scene in the 1990s, and ARB inhibitors, like Novartis' (NYSE:NVS) Diovan, which won approval in 1997, remain first line therapies in the fight to prevent heart disease.

However, despite those medicines being widely prescribed, high blood pressure remains inadequately treated and that means a greater percentage of people suffer heart failure every year. Estimates suggest that as many as 50% of those who should be taking drugs that lower blood pressure don't take them and discouragingly, only a third of those who do take them have their blood pressure under adequate control.

Fortunately, a new drug making its way to regulators from Novartis may offer patients new hope. This past weekend, Novartis released full study results from phase 3 trials of LCZ696, a combination therapy that is made up of the company's Diovan and a new drug, AHU-377.

Source: Novartis

A changing market
According to Express Scripts, high blood pressure is the third highest cost indication behind diabetes and high cholesterol, but spending on ACE inhibitors and ARBs is expected to fall through at least 2016 due to the launch of new generic versions of the blockbuster Diovan.

Express Scripts thinks that generic Diovan will be just as successful as generic ACE inhibitors like lisinopril, which was formerly marketed by Merck and AstraZeneca. Lisinopril is among the most widely prescribed drugs in America, accounting for 16.6% market share of all high blood pressure medication.

If Express Scripts forecast is correct, switching to generic Diovan will result in spending on high blood pressure drugs falling 12% this year and another 11% more in both 2015 and 2016.

Source: Novartis

A new option
Novartis hasn't been shy in its attempts to broaden its Diovan franchise by developing combination therapies. Its Diovan HCT pairs up Diovan with a water pill and that drug pulled in sales of more than $1.5 billion a year before losing patent protection in 2012.

Novartis' Exforge, a combination of Diovan and a calcium channel blocker -- another popular blood pressure lowering medication -- has also been a big seller. Exforge sales totaled $1.4 billion last year; however, Exforge loses patent protection next month.

Rapidly falling sales for Diovan HCT, Diovan, and (soon) Exforge, Novartis is pinning hope on LCZ696, which matches up Diovan with AHU-377, a neprilysin enzyme inhibitor that stops the enzyme from damaging blood pressure-lowering peptides.

In phase 2 trials, patients receiving LCZ696 instead of Diovan had better control over their hypertension and a strong showing in phase 3 trials prompted independent monitors to halt the late stage study early.

This past weekend, Novartis presented the data behind the monitor's decision and that data may be compelling enough to turn LCZ696 into a blockbuster.

In the phase 3 trial, LCZ696 faced-off against enalapril and over a 27 week period, patients receiving LCZ696 showed both a lower rate of death and a lower rate of hospitalization for heart failure. Overall, 21.8% of those taking LCZ696 either died or had been hospitalized due to their condition, versus 26.5% for those taking enalapril.

Fool-worthy final thoughts
That 20% improvement is significant enough that Novartis plans to file for U.S. approval of LCZ696 later this year and European approval early next year.

Since there has been little improvement in drug therapy since Diovan, LCZ696 may find that both doctors and patients willingly embrace it. If that proves true, LCZ696 will go a long way to sure-ing up Novartis' sales in the face of mounting generic competition.

Todd Campbell has no position in any stocks mentioned. Todd owns E.B. Capital Markets, LLC. E.B. Capital's clients may or may not have positions in the companies mentioned. Todd owns Gundalow Advisors, LLC. Gundalow's clients do not have positions in the companies mentioned. The Motley Fool has no position in any of the stocks mentioned. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.