Bust out the brooms; Amgen's (NASDAQ:AMGN) evolocumab has swept its phase 3 program so far.

In the last month and a half, the biotech has announced positive results for four phase 3 trials for the cholesterol-lowering drug. One trial combined evolocumab with statins in patients with high cholesterol. Another tested evolocumab in patients who couldn't take statins. The third trial placed patients on the drug for a year as a test of safety. And the fourth tested patients who were not receiving any lipid-lowering therapy prior to entering the trial.

On Thursday, Amgen announced positive results for two more trials.

One trial tested patients with heterozygous familial hypercholesterolemia. These patients have a mutation in one of the two copies of genes in the cholesterol pathway. While not as bad as the homozygous form in which patients have two mutated copies, patients with heterozygous familial hypercholesterolemia have high cardiovascular risk due to high cholesterol levels.

Adding evolocumab to statins and other lipid-lowering drugs helped patients lower their bad LDL cholesterol compared to placebo plus other therapies.

Almost as an aside -- because it's not nearly as important -- Amgen also said that a usability study testing patient's ability to self-administer an injection of evolocumab was also successful. One of the treatment regimens calls for dosing every two weeks, so not having to go into the doctor's office twice a month would be a huge advantage.

There are 13 phase 3 trials in Amgen's evolocumab program, so we're almost halfway to the finish line. Amgen intends to apply for FDA approval later this year.

Positive, but by how much?
Besides telling investors that the drug passed its primary endpoints of reducing bad cholesterol, the press release didn't have any actual efficacy data: "The mean percent reductions in LDL-C, or "bad" cholesterol, were consistent with the results observed for the same doses in the Phase 2 Rutherford trial for evolocumab compared to placebo."

A pessimist would argue that Amgen is trying to hide something by calling the data "consistent." More likely, though, the company is just saving the data for a medical conference where it can have more impact. Amgen is large enough that it can get away with holding back data even if investors -- and Foolish writers -- don't like it.

In the lead
Evolocumab targets proprotein convertase subtilisin/kexin type 9, or PCSK9, a protein that reduces the liver's ability to remove bad cholesterol from the blood. Amgen isn't the only company going after the target, though.

Regeneron Pharmaceuticals (NASDAQ:REGN) and Sanofi (NASDAQ:SNY) are developing alirocumab, which is in phase 3 development. If everything goes as planned, Regeneron and Sanofi could apply for FDA approval next year, giving Amgen about a year's head start.

There is plenty of additional competition as well. Pfizer, Roche, Merck, Eli Lilly, and Alnylam Pharmaceuticals (NASDAQ:ALNY) also have PCSK9 inhibitors in development. Alnylam's drug, ALN-PCS, is an interesting one to watch because it uses RNAi to inhibit the production of PCSK9 rather than antibodies like evolocumab and Reneron and Sanofi's alirocumab that bind to the PCSK9 protein after it is produced. While much further back in the clinic, it could theoretically have higher efficacy.

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