When Amgen (AMGN -0.21%) reports fourth quarter results next week, investors will probably find that revenue will be supported by rising sales for its osteoporosis drugs Xgeva and Prolia.  Based on last quarter's results, the drugs' combined sales look set to reach $1.5 billion in annual sales.

This success is impressive, but, as long-term investors, it's also important to watch what Amgen says about its late stage cholesterol lowering drug AMG-145. The company is in a tight race, as this experimental drug could face competition from medications in development at Sanofi (SNY -0.94%) and its partner Regeneron (REGN 0.45%), and big pharma company Pfizer (NYSE: PFE).

A new way to fight cholesterol
Statins designed to lower cholesterol and reduce cardiovascular risk have been among the industry's biggest sellers over the past twenty years. Annual spending on statins reached nearly $20 billion in 2005, creating a slate of blockbuster treatments including Pfizer's multi-billion dollar drug Lipitor.

But it is PCSK9 inhibitors like AMG-145, also known as evolocumab, which may dethrone statins and dominate high cholester treatment sales this decade. Because these drugs prevent the PCSK9 protein from reducing the liver's ability to remove bad cholesterol from a patients blood, they represent an entirely new class of cholesterol fighting compounds.

So far, this cholesterol busting approach appears to be working. AMG-145 put up impressive results during phase 2 trials with the average patient seeing LDL fall by 40% to 59% versus just 0.1% to 0.5% for placebo. That mid-stage success is backed up by recently reported trial data studying the drug in patients unable to take statins because of muscle-related side-effects. In this phase 3 study, AMG-145 met its co-primary endpoints for lowering bad cholesterol at week 12 and lowering average cholesterol at week 10 and 12.

In addition to comparing AMG-145 to placebo in the study, Amgen also dosed AMG-145 alongside and up against Merck's $2 billion-a-year Zetia, another cholesterol fighting drug used in statin intolerant patients. Patients treated with AMG-145 had fewer headaches and muscle pain than the Zetia arm, but reported a higher incidence of pain in extremities and muscle spasms.  

Amgen isn't reporting the actual percent reduction in cholesterol yet, but it did indicate the results were similar to phase 2 across those who can't take statins. That suggests a roughly 51% reduction in LDL when used alone and a 63% average reduction when combined with Zetia.

Those results follow equally compelling phase 3 data presented by Amgen in December, which demonstrated that AMG-145 lowered bad cholesterol in patients who aren't taking other cholesterol reducing therapies.

Racing to market
A study conducted by the American Heart Association estimates Americans will spend three times more treating cardiovascular disease in 2030 than they spent in 2010 as the percentage of people affected by it climbs to 40% of the population. Since spending is expected to eclipse $800 billion over the period, demand for therapies that may reduce the risk of cardiovascular disease is likely to jump.

How much demand climbs and how willing patients and insurers are to pay for it remains a question, but given Lipitor racked up $125 billion in sales between 1997 to 2011, there's clearly big money at stake for whichever PCSK9 therapy can post the best results.

As a result, Amgen isn't the only one advancing PCSK9 protein inhibiting drugs through its pipeline. Sanofi and Regeneron's competing drug alirocumab reduced LDL levels in 94% of patients during phase 3. And Pfizer is working on its own PCSK9 compound, RN316.

In trials, Sanofi and Regeneron's alirocumab lowered bad cholesterol by 47% after 24 weeks and Pfizer's RN316 lowered it by 56% after 12 weeks.

Fool-worthy final thoughts
Amgen, Sanofi/Regeneron, and Pfizer are studying their drugs in thousands of patients across dozens of late stage trials in a bid to outmaneuver one another.  Sanofi and Regeneron have 12 studies under way, Pfizer plans to enroll 22,000 patients in studies of its RN316, and Amgen is conducting 13 phase 3 trials for AMG-145.  

That suggests investors will have a flood of PCSK9 data to digest over the coming two years and plenty of market moving presentations to pour over when results are presented at the American College of Cardiology Meeting in March.