With a near-certain approval of Regeneron Pharmaceuticals' (Nasdaq: REGN) macular degeneration treatment Eylea on the horizon, investors can turn to other drugs farther back in the pipeline. This week, the company released data for its autoimmune disease treatment sarilumab.

In a phase 2b trial, the drug proved successful in treating rheumatoid arthritis, with 72% of patients taking the higher dose in combination with methotrexate reporting at least a 20% improvement in symptoms. Only 46% of patients taking methotrexate alone reported the same level of improvement. A lower dose had a modest and probably meaningless increase with 49% of patients reporting at least a 20% improvement.

In a separate trial, Regeneron and partner Sanofi said that sarilumab failed to show an effect in patients with another autoimmune disease called ankylosing spondylitis. It looks like sarilumab is off to a phase 3 in just rheumatoid arthritis.

But the phase 3 trial might not be the biggest hurdle for sarilumab. Like Eylea, which will compete with Roche's Lucentis and Avastin, sarilumab will hit plenty of competition if it makes it to market.

To make a dent in the market, sarilumab needs to have better efficacy than the established autoimmune players that target TNF: Merck (NYSE: MRK) and Johnson & Johnson's (NYSE: JNJ) Remicade, Abbott Labs' (NYSE: ABT) Humira, and Enbrel from Amgen (Nasdaq: AMGN) and Pfizer (NYSE: PFE).

Sarilumab targets a different molecule, the IL-6 receptor, but competition is heating up there, too. Roche's Actemra is already approved, and Alder Biopharma and Bristol-Myers Squibb (NYSE: BMY) are developing an IL-6 inhibitor called ALD518.

If you add in potential oral rheumatoid arthritis medications from Pfizer and others, Regeneron and Sanofi look like they'll need out-of-this-world data for sarilumab for sales to amount to much.

Interested in keeping track of Regeneron as it gains approval of Eylea and develops the rest of its pipeline? Click here to add it to My Watchlist, which will help you keep track of all our Foolish analysis on Regeneron.

Fool contributor Brian Orelli holds no position in any company mentioned. Click here to see his holdings and a short bio. The Motley Fool owns shares of Johnson & Johnson and Abbott Laboratories. Motley Fool newsletter services have recommended buying shares of Abbott Laboratories, Pfizer, and Johnson & Johnson, as well as creating a diagonal call position in Johnson & Johnson. 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.