Amgen (AMGN 0.71%) topped earnings expectations in both first and second quarters of 2016. The big biotech gets a shot at sustaining the trend when it announces its third-quarter results on Oct. 27. Here are three questions the company should answer that will make the difference in whether or not Amgen makes it three in a row.

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1. How well did the "big six" perform?

Nearly three-quarters of Amgen's total revenue comes from six drugs. Autoimmune disease drug Enbrel leads the pack, generating close to $1.5 billion in the second quarter. The good news for Amgen is that sales for the drug continue to grow at a solid pace. The not-so-good news, however, is that most of Enbrel's year-over-year growth last quarter came from price increases rather than higher volume. Sooner or later, it will probably become more difficult for Amgen to boost sales by price hikes.

The only member of the "big six" to see lower sales in the second quarter compared with the prior-year period was Neulasta. That decline was small, though. Amgen's final patent for the bone marrow stimulant expired at the end of 2015. Sales will probably continue to fall, but that shouldn't hurt Amgen too much, thanks to the rest of the biotech's products.

Bone disease drugs Prolia and Xgeva should continue to be the rock stars of Amgen's lineup. Both drugs experienced strong year-over-year growth in the second quarter. Sales for Aranesp, on the other hand, grew by only 5% in the second quarter versus the prior-year period. Watch especially to see if international sales for the bone marrow stimulant improve.

2. Is Repatha picking up momentum?

Amgen's new cholesterol drug, Repatha, could ultimately become one of its biggest sellers. In the second quarter, though, Repatha's sales totaled only $27 million. Investors will definitely be encouraged if Repatha picks up momentum in the third quarter.

A big obstacle right now is that payers have implemented utilization-management processes that made it harder for patients to get Repatha. This isn't an issue affecting just Amgen, though.

Regeneron (REGN 0.50%) and Sanofi (SNY 1.53%) market Praluent, which, like Repatha, belongs to the new class of cholesterol drugs known as PCSK9 inhibitors. Praluent generated sales of $24 million in the second quarter -- pretty much in line with Repatha.

The payer barriers for Repatha and Praluent could be torn down, however, if results from cardiovascular outcomes studies prove to be positive. Amgen expects to announce its cardiovascular outcomes study for Repatha in the first quarter of 2017. Regeneron and Sanofi won't announce their results until late 2017.

3. Did the downward cost trends continue?

It's sometimes easy for investors to get so caught up in product sales that we forget the other critical component for achieving great earnings results: controlling costs. This is an area in which Amgen has excelled recently.

The biotech's cost of goods sold actually decreased in the second quarter compared with the prior-year period. Amgen chalks this improvement up to the efficiency and productivity of its manufacturing operations. The only operating expense that did increase year over year in the second quarter was research and development (by only 11%). If Amgen can continue to keep costs on a downward trajectory while increasing sales, it should beat earnings expectations yet again.