GlaxoSmithKline (GSK 0.97%) hasn't been spared the market sell-off caused by the COVID-19 pandemic. Year to date, the company's shares are down by 19%, and the healthcare giant is currently hovering near a five-year low. Also, GlaxoSmithKline is trading at just 12.4 times future earnings, and the company's forward price-to-earnings-growth (PEG) ratio is only 0.5. Given these attractive valuation metrics, should investors consider buying shares of the London-based pharmaceutical company?

GlaxoSmithKline's diversified business

GlaxoSmithKline generates the bulk of its revenue from its biopharma business. However, this segment has not performed particularly well of late. During the fourth quarter, the company's pharmaceutical sales were 4.6 billion pounds, a 5% year-over-year decrease. This decrease was because several of GlaxoSmithKline's products lost steam; for instance, HIV drug Tivicay recorded quarterly sales of 426 million pounds, down 6% year-over-year, and another HIV drug, Triumeq, posted 638 million pounds in sales, down 8%. 

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Also, sales of Breo Ellipta -- which treats the symptoms of asthma and prevents asthma attacks -- were 269 million pounds during the fourth quarter, a 19% decrease compared with the year-ago period. GlaxoSmithKline does expect other products to help sales from its biopharma business, which it expects to pick up in the coming quarters. The company currently has 39 products in development that are seeking new (or additional) indications.

For instance, in February, the U.S. Food and Drug Administration accepted GlaxoSmithKline's supplemental New Drug Application for Zejula as a treatment for a form of advanced ovarian cancer. Zejula is already approved for several types of cancer, and GlaxoSmithKline plans on widening Zejula's addressable market by submitting it for review as a treatment for lung and breast cancer. In short, the company has big plans for Zejula. 

Furthermore, GlaxoSmithKline can rely on its two other segments to keep its sales afloat. During the fourth quarter, the company's vaccine business recorded sales of 1.7 billion pounds -- an 18% year-over-year increase -- while its consumer healthcare business reported sales of 2.8 billion pounds, 35% higher than the year-ago period. Thanks to the performance of these two businesses, GlaxoSmithKline recorded total sales of 8.9 billion pounds for the fourth quarter, an 8% year-over-year increase.

Within GlaxoSmithKline's vaccine segment, the company's shingles vaccine recorded sales of 532 million pounds, more than doubling its sales compared with the fourth quarter of 2018. Meanwhile, GlaxoSmithKline's meningitis vaccine franchise recorded sales of 203 million pounds, an 8% year-over-year increase. The company currently has 15 vaccines in its pipeline, and this segment will likely continue to spur GlaxoSmithKline's sales growth moving forward.

Going through a transition

GlaxoSmithKline is in the process of splitting into two separate companies, one of which will be GSK Consumer Healthcare, a joint venture GlaxoSmithKline formed with Pfizer (PFE -2.63%) in a transaction that closed in August of last year; GlaxoSmithKline owns a 68% stake in GSK Consumer Healthcare. GlaxoSmithKline will also create a biopharma-focused entity called New GSK. The company expects this move to reduce its expenses, improve its margins, and, ultimately, improve its bottom line. 

Looking forward

GlaxoSmithKline will likely see modest revenue growth in the next few quarters, and the company expects its adjusted earnings per share (EPS) to decrease slightly for fiscal year 2020, even without taking into account the potential impact of the COVID-19 pandemic. Also, the company's stock may experience a lot of volatility in the short term because of the ongoing outbreak and its own internal changes. For those reasons, I think investors had better stay away from the healthcare giant, at least until its transformation fully takes form.