Source: Hillary Clinton via Facebook.

A tweet by Presidential-hopeful Hillary Clinton lambasting sky-high drug prices and promising plans for reform led to biotech stocks losing $40 billion in market cap in a matter of hours, according to Bloomberg.

Let's take a look at what companies got hit the hardest.

1. Ultragenyx Pharmaceuticals (RARE -1.65%) -- down 13.9%
Some of the globe's most expensive medicines are for the treatment of rare diseases, and given the increasing scrutiny of exorbitant prices, it's probably not too surprising to learn that shares in the clinical-stage rare-disease drug developer Ultragenyx Pharmaceuticals toppled nearly 14% yesterday after Clinton's tweet.

The company is working on therapies for underresearched diseases including X-linked hypophosphatemia, an inherited bone disease, and mucopolysaccharidosis 7, or Sly syndrome, a genetic metabolic disorder.

Despite the company's research remaining in the early stages of clinical testing, investors have flocked to its shares in hopes that its rare-disease drugs could command similar six-figure annual prices that are currently paid for enzyme replacement therapies for other rare diseases. Although therapies for Fabry disease cost roughly $200,000 per year and a common treatment for mucopolysaccharidosis type VI costs $365,000 per year, Clinton's comments throw cold water on the likelihood that Ultragenyx could be able to price its drugs similarly someday.

2. Juno Therapeutics (JUNO) -- down 10.9%
Juno Therapeutics inked a billion-dollar deal with Celgene Corp. this summer to collaborate on next-generation cancer drugs, but its shares got clobbered yesterday because cancer drugs have become increasingly more expensive and thus could be a target of price controls.

Since 2014, seven of eight cancer drugs approved by the FDA for use in the U.S. have been priced near or above $10,000 per month, including immuno-oncology drugs, according to the Memorial Sloan Kettering Cancer Center.

Because Juno's most advanced drug in clinical trials is JCAR015, a chimeric antigen receptor immuno-oncology therapy that reengineers a patient's T-cells to find and destroy cancer cells, investors are right to wonder whether price curbs could make Juno less valuable, especially since Juno's approach is complex and therefore costly and its market cap is $4 billion -- an arguably rich price to pay for a company without any drugs on the market.

3. Lexicon Pharmaceuticals (LXRX 0.62%) -- down 10.1%
Lexicon Pharmaceuticals shares have been riding high since the company reported positive phase 3 trial results for telotristat etiprate, a therapy for the treatment of carcinoid syndrome.

Carcinoid syndrome is caused by a rare carcinoid tumor that secretes chemicals, including serotonin, into a patient's bloodstream, resulting in a series of symptoms, including frequent diarrhea. Unfortunately, there's a significant unmet need for new approaches for use in patients whose symptoms are uncontrolled by current treatment options, and for that reason, the FDA has awarded Lexicon both fast-track and orphan drug status on this drug. 

Those designations could mean that Lexicon's drug gets to the market more quickly, and if so, telotristat etiprate could become an important treatment option for patients who don't respond to high-price somatostatin analogues, such as sandostatin, a drug made by Novartis that is on pace to rack up over $1.5 billion in annual sales this year and costs $2,466 for a 30mg dose.

If price controls mean that Lexicon can't price telotristat etiprate similarly to sandostatin, then Lexicon's shares may not be worth as much as people had been thinking, which is why its shares slumped yesterday.

Tying it together
All three of these companies are developing drugs for markets that support high-priced drugs, but investors may not want to worry too much about Clinton's plan and its impact on companies crafting new drugs for tough-to-treat conditions -- at least not yet.

Certainly, Clinton's plan to limit patient copays and give Medicare more negotiating power could create headwinds for these companies, but there's far more incentive for policymakers to focus their attention on curbing the prices being paid for drugs that are already on the market, but have recently been rebranded and relaunched with significant price increases, than risk stifling innovation among companies targeting rare and life-threatening diseases.

Regardless, investors who are considering selling healthcare stocks because of Clinton's views may want to remember that many people fretted over the Affordable Care Act's impact on the healthcare sector, but it has increased, rather than reduced, healthcare profitability. Also, it may help to keep in mind that presidential candidates often aim high with their policies during election years, but those often change significantly if they ever make their way to Capitol Hill.

Overall, that suggests that focusing more on the long-haul trend of growing demand tied to a larger, longer-living population than the latest political whims and whispers on the campaign trail may be the best long-term strategy.