Roche (NASDAQOTH:RHHBY) recently agreed to buy Spark Therapeutics (NASDAQ:ONCE) for a whopping 150% premium over its previous day's closing price, and investors want to know which gene therapy stocks could be next to receive a buyout offer from a big pharma with plenty of cash. 

The announcement pushed up shares of at least half a dozen companies with gene-editing programs. Although Roche's big investment is a plus for the entire field, some biotechs have a better chance of receiving a juicy buyout offer than others.

Biomarin Pharmaceutical (NASDAQ:BMRN) and uniQure (NASDAQ:QURE) don't receive as many headlines as their younger peers do, but they have programs in late-stage development that some big pharmas will find hard to resist. 

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Here's what sparked Roche's interest

To understand what makes UniQure and Biomarin more attractive than their gene-editing peers, we need to understand why Roche splurged for Spark Therapeutics. The Swiss pharma giant's main motivation was to head off a potential threat to a new hemophilia treatment that could earn $4 billion annually by 2022.

In 2017, Roche launched Hemlibra, the first easily injectable treatment that helps hemophilia A patients prevent bleeding episodes. At the moment, most patients still receive clotting factor replacement therapy through an intravenous infusion multiple times each week, and the expenses really add up. Roche priced Hemlibra at around $450,000 annually, and an independent industry watchdog, the Institute for Clinical and Economic Review, still thinks it can save end payers around $1.85 million per adult patient every year.

Hemlibra already has big pharmas with significant hemophilia sales nervous, and Roche's step into the gene therapy arena could be the extra push needed to make a big acquisition.  

1. uniQure: Getting over Glybera 

In 2012, UniQure became the first company to launch a gene therapy, called Glybera, but had to pull it from the European market because it was a complete commercial failure. Glybera carried a million-dollar price tag, and the therapy was aimed at an ultra-rare disorder. UniQure's new lead candidate, AMT-061, has a much better chance at commercial success as a treatment for hemophilia B, which affects an estimated 20,000 people in the U.S. alone.

UniQure's lead candidate, AMT-061, helped three out of three hemophilia B patients produce enough clotting factor to reduce their need for replacement therapy 12 weeks after receiving their first and only dose. In February, the company treated the first of 50 patients in a pivotal study that will measure their ability to produce their own clotting factor after waiting six months, one year, and five years.

At recent prices, UniQure sports a $2.1 billion market cap, which puts it in range for dozens of biopharma's larger members. Takeda might be stretched a bit too far after a record-setting $62 billion merger with Shire last year to make another purchase in the near term, but investors should know that hemophilia treatments were a key attraction that brought the Japanese pharmaceutical giant to the deal table.

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2. BioMarin Pharmaceutical: The perennial favorite

BioMarin is becoming a euphemism for "top buyout candidate that never gets bought," but a heightened interest in hemophilia could do the trick in 2019. BioMarin markets a handful of rare-disease drugs with combined annual sales that rose 14% last year to $1.5 billion, and a potential new gene therapy for hemophilia A patients is getting close to the finish line.

After showing the FDA some breathtaking early results for an experimental gene therapy called valrox (valoctocogene roxaparvovec) last year, BioMarin began enrolling more patients into a special cohort designed to support an application for accelerated approval. The FDA wants to see clotting factors from the larger cohort reach levels seen with the same dose in a small group of patients.

BioMarin won't finish enrolling and observing baseline patient data in the third quarter, but we should know if the results might be good enough to support a new drug application before the end of 2019. 

A scientist using a pipette.

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As a commercial-stage company with significant sales, BioMarin is too expensive for most suitors. That almost includes Sanofi (NASDAQ:SNY), a big pharma eager to boost its presence in the rare-disease space, and hemophilia specifically. 

About a year ago, Sanofi shelled out a whopping $11.6 billion for Biogen's hemophilia spinoff, Bioverativ, and received Eloctate for hemophilia A patients plus Alprolix for the much smaller hemophilia B population in the process. In the fourth quarter, Eloctate sales rose 4.3% to $223 million, which is a lot slower than Sanofi investors were expecting a year ago. A merger with BioMarin could be exactly what the French pharma giant's new rare-disease segment needs.

What if there are no more offers?

Predicting future mergers and acquisitions is so difficult that you should never buy a stock simply because it might be acquired at a premium. While UniQure's price range makes it more likely to receive a buyout offer, you might be better off with shares of BioMarin. After all, the company's expecting $2 billion in annual sales next year, even if its gene therapy gamble comes up snake eyes.