Source: Pfizer via Facebook

What: Despite a busy month during which U.S. regulators approved its acquisition of biosimilars drug developer Hospira and the company announced the acceptance of its application for approval of the cancer drug Ibrance in the EU, shares in Pfizer, Inc (PFE 1.06%) slumped 10% in August.

So what: Pfizer's Hospira and Ibrance news were unable to trump an industry wide sell-off that saw the S&P Pharmaceuticals index ETF tumble by 11.5%.

Following the patent expiration of its top-selling cholesterol lowering drug Lipitor in 2011, sagging sales led to a slate of lackluster years for Pfizer. However, up until August, shares had been marching steadily higher this year on hopes that a corner is turning for the company.

In July, the Goliath pharmaceutical company gave credence to that argument by reporting its third consecutive quarter of positive year-over-year operational growth and bumping up the low end of its full year 2015 sales forecast by $1 billion to $45 billion and boosting its full year EPS outlook to at least $2.01, up from prior estimates for at least $1.95.

In August, Pfizer followed up those solid second quarter results by announcing U.S. regulators had cleared its Hospira buyout, effectively launching Pfizer to the forefront of the emerging market for generic alternatives to pricey biologic drugs.

Hospira's promising pipeline of these generic alternatives to biologics, which are known as biosimilars because they aren't exact copies but work similarly to the underlying therapy, positions Pfizer to capture a significant share of the biosimilar market, which is expected to grow from $3 billion this year to $20 billion in 2020.

Pfizer also made headway when EU regulators accepted an application for the breast cancer drug Ibrance's approval last month. If Pfizer secures EU approval for Ibrance it could be significant because an approval in the U.S. in February led to sales of $140 million during Ibrance's first full quarter on the market.

Now what:  Because Pfizer's sell-off makes shares even more reasonably priced than they were in July before it announced second quarter EPS, investors might want to consider it for portfolios. After all, Pfizer is trading at just 13.5 times next year EPS forecasts and if currency headwinds abate, biosimilars demand takes off, and fast-growing drugs like Ibrance gain traction, then that price may be a bargain, especially since shares are paying a 3.48% forward dividend yield.