When the future looks bright for a drugmaker, investors are willing to shrug off a quarter of slow top-line growth. This appears to be the case with MGI Pharma (NASDAQ:MOGN), which last week announced less than double-digit top-line growth in the second quarter but still had shares tick up a bit following the news.

Revenue grew less than 7% in the second quarter year over year as a result of lead drug Aloxi indirectly being affected by generic versions of a competing drug, Zofran, produced by GlaxoSmithKline (NYSE:GSK). Like Aloxi, Zofran and its generic knockoffs also treat chemotherapy-induced nausea and vomiting.

Sales of Aloxi fell 28% versus the second quarter last year but are expected to begin rising again in the third quarter as the generic competition against it slows down because of the lowering of reimbursement rates for the generic competitors. MGI currently has a supplemental New Drug Application to expand the drug's label to also treat post-operative nausea pending review with the FDA, and an oral version of the drug is also in clinical testing.

If it is successful on some of these fronts, then MGI estimates that Aloxi sales in just the chemotherapy-induced nausea indication could jump from last year's $250 million, all the way up to $500 million in peak annual sales. That's a lot of dough for a drugmaker whose total sales for all its compounds were $340 million last year

The other compound that accounts for the majority of MGI's sales is myelodysplastic syndrome treatment drug Dacogen, which entered the market in the middle of last year. Dacogen sales gained a healthy 31% versus the first quarter of this year, to $30 million. Based on the drug's sales growth, MGI raised its full-year sales estimates for Dacogen to $115 million.

Drugmakers like MGI that carve out a profitable niche treating non-blockbuster indications often get overlooked by investors and can often truly be called the rare pharmaceutical value stocks. If MGI can expand the market for Aloxi and continue its strong Dacogen sales growth, then it has more good days ahead.

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Fool contributor Brian Lawler does not own shares of any company mentioned in this article. The Fool has a disclosure policy. GlaxoSmithKline is an Income Investor recommendation.