NEW YORK ( TheStreet) -- A lot of investors are obsessed with the question of "Will Sarepa Therapeutics ( SRPT) receive accelerated approval for eteplirsen?" The focus on the outcome of this month's meeting between Sarepta and FDA is understandable but misses a broader point: Sarepta at its current stock price is undervalued even if eteplirsen accelerated approval is not granted. My biggest worry as a Sarepta shareholder used to be that eteplirsen wouldn't receive accelerated approval, allowing GlaxoSmithKline ( GSK) to reach the U.S. market first with its competing Duchenne muscular dystrophy (DMD) drug drisapersen. But now that safety questions have been raised about drisapersen, it is more apparent that eteplirsen will be the market leader even if FDA approval isn't granted for another three years. Eteplirsen is likely a $500 million-plus market opportunity for Sarepta in the U.S., which has only about 2,000 patients with the missing exon-51 gene. This captures 6% of the total DMD patient population. The same exon-skipping drug technology can be used to treat other forms of the disease. Sarepta's next four targets encompass about 9,000 patients. If you count all the the patients that could benefit from exon-skipping drugs, the total is near 30,000. Sarepta has already received notice from the FDA that at some point they will not have to do a separate clinical trial for each exon-skipping drug (Although FDA first wants to see separate, successful data on the first three or four targets.) Sarepta is expected to start new clinical trials by early next year. Let's take a look at a reasonable scenario that assumes no accelerated approval for eteplirsen: The drug reaches the U.S. market in early 2016 and three new exon-skipping targets -- 45, 50 and 53 -- are approved in 2017. This gives Sarepta a market opportunity totaling 7,000 patients in four years. Let's assume a price of $350,000 (on the lower side of estimates) and a capture rate of 70% by 2019. That would give Sarepta $1.7 billion in sales in six years time. Keep in mind that these 7,000 patients are only one-quarter of the addressable market. Once it dawns on investors that Sarepta's exon-skipping technology works in the first few targets, the company's market value will begin to bake in other targets as well. Alexion Pharmaceuticals ( ALXN) generated a bit less than $1.2 billion in sales in 2012 by selling the ultra-orphan drug Soliris. Alexion's market cap: $17 billion. Biomarin Pharmaceuticals ( BMRN), another ultra-orphan drug marketer with only $500 million in annual revenue (but the opportunity to double that in a few years) has a market cap of over $7 billion. Today, Sarepta's market cap stands at $800 million. If one assumes a similar market cap as Alexion in six years time, Sarepta has the potential to be a 20-bagger -- if my scenario plays out. I first bought Biomarin seven years ago when its market value was similar to Sarepta today. Owning Biomarin required some patience but the stock is up five fold since I first invested. Accelerated approval or not, Sarepta has the potential to move much higher in the years to come, if the company's exon-skipping technology can prove to treat DMD effectively and safely. Rosenblum is long Sarepta and Biomarin.