Mersana Therapeutics, Inc. (NASDAQ:MRSN) shares have had a horrible month, losing 25% after a relatively good period beforehand. The drop over the last 30 days has capped off a tough year for shareholders, with the share price down 31% in that time.

Following the heavy fall in price, Mersana Therapeutics' price-to-sales (or "P/S") ratio of 5.7x might make it look like a buy right now compared to the Biotechs industry in the United States, where around half of the companies have P/S ratios above 9.9x and even P/S above 60x are quite common. However, the P/S might be low for a reason and it requires further investigation to determine if it's justified.

How Has Mersana Therapeutics Performed Recently?

Mersana Therapeutics could be doing better as its revenue has been going backwards lately while most other companies have been seeing positive revenue growth. It seems that many are expecting the poor revenue performance to persist, which has repressed the P/S ratio. If this is the case, then existing shareholders will probably struggle to get excited about the future direction of the share price.

Do Revenue Forecasts Match The Low P/S Ratio?

The only time you'd be truly comfortable seeing a P/S as low as Mersana Therapeutics' is when the company's growth is on track to lag the industry.

Taking a look back first, the company's revenue growth last year wasn't something to get excited about as it posted a disappointing decline of 15%. The latest three year period has seen an incredible overall rise in revenue, a stark contrast to the last 12 months. Therefore, it's fair to say the revenue growth recently has been superb for the company, but investors will want to ask why it is now in decline.

Looking ahead now, revenue is anticipated to slump, contracting by 2.1% each year during the coming three years according to the ten analysts following the company. With the industry predicted to deliver 115% growth per annum, that's a disappointing outcome.

With this information, we are not surprised that Mersana Therapeutics is trading at a P/S lower than the industry. Nonetheless, there's no guarantee the P/S has reached a floor yet with revenue going in reverse. There's potential for the P/S to fall to even lower levels if the company doesn't improve its top-line growth.

What We Can Learn From Mersana Therapeutics' P/S?

Mersana Therapeutics' recently weak share price has pulled its P/S back below other Biotechs companies. We'd say the price-to-sales ratio's power isn't primarily as a valuation instrument but rather to gauge current investor sentiment and future expectations.

With revenue forecasts that are inferior to the rest of the industry, it's no surprise that Mersana Therapeutics' P/S is on the lower end of the spectrum. Right now shareholders are accepting the low P/S as they concede future revenue probably won't provide any pleasant surprises. It's hard to see the share price rising strongly in the near future under these circumstances.

Before you take the next step, you should know about the 3 warning signs for Mersana Therapeutics that we have uncovered.

Of course, profitable companies with a history of great earnings growth are generally safer bets. So you may wish to see this free collection of other companies that have reasonable P/E ratios and have grown earnings strongly.

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