Growth-oriented investors looking for stocks that can heat up their portfolios before the end of 2023 want to turn their attention to the healthcare sector. Upcoming binary events could soon send these two biotech stocks rocketing higher. 

The U.S. Food and Drug Administration (FDA) is scheduled to make some important approval decisions before the end of the year. A positive result could send shares of the drugmakers involved soaring, but there are no guarantees. Here's what you should know about these volatile stocks and their upcoming catalysts.

Alnylam

Alnylam (ALNY -0.14%) develops drugs made from small strands of RNA that interfere with the production of troublesome proteins. The company's first treatment, Onpattro, halts the production of a protein called transthyretin before it can unravel and form amyloid plaques that damage peripheral nerves, the heart, and other organs.

Five years ago, Onpattro earned FDA approval to treat the relatively small population of patients with polyneuropathy caused by hereditary transthyretin-mediated amyloidosis (hATTR). The stock could soar if the FDA approves a pending application to treat a much larger population of patients with hATTR cardiomyopathy.

An expansion of Onpattro's prescribing label to include the hATTR cardiomyopathy population could do a lot to widen Alnylam's revenue stream. In 2019, the FDA approved Pfizer's Vyndaqel for the treatment of ATTR cardiomyopathy, and it's already on pace to generate $3.1 billion in annual revenue.

The FDA was supposed to announce its approval decision on or before Oct. 8. The FDA rarely makes weekend announcements, so effectively, the agency was expected to announce by close of business on Friday, Oct. 6. At the time of writing, Oct. 7, the agency still hadn't issued its decision or asked for more time.

While Alnylam stock could soar if the FDA approves Onpattro for hATTR cardiomyopathy, a positive approval decision is far from certain. In September, an independent panel of experts voted 9-to-3 when asked if its benefits outweighed its risks for this population.

Alnylam has a more recently launched treatment for hATTR polyneuropathy patients called Amvuttra. Pivotal data from a trial with Amvuttra and hATTR cardiomyopathy patients is expected early next year. I won't be surprised if the FDA delays Onpattro's cardiomyopathy application indefinitely and then approves an upcoming one for Amvuttra near the end of 2024.

2Seventy Bio

Back in 2021, 2Seventy Bio (TSVT 11.33%) and its collaboration partner, Bristol Myers Squibb (BMY -1.13%), earned FDA approval for Abecma. It's the first approved cellular therapy for advanced-stage multiple myeloma patients, but the FDA limited its approval to a narrow population with disease that has persisted after four or more previous lines of treatment.

Abecma finished the second quarter on pace to generate between $470 million and $570 million in sales this year. 2Seventy Bio and Bristol Myers Squibb share equally in profits and losses, but 2Seventy still lost $42 million in the second quarter.

2Seventy thinks U.S. Abecma sales could explode to more than $2 billion annually if it's approved to treat a wider patient population. On or before Dec. 16, the FDA is expected to issue a decision based on results of the KarMMa-3 trial with multiple myeloma patients who relapsed after two to four lines of treatment.

A positive approval decision seems likely. Treatment with Abecma reduced patients' risk of disease progression or death by 51% compared to standard care. 

If Abecma sales don't pick up and drive 2Seventy's bottom line toward profitability soon, investors could suffer heavy losses. The company finished June with $306.5 million in cash after operations lost $99.7 million in the first half of the year. Before loading your portfolio up with shares of 2Seventy Bio, you should understand this investment is only appropriate for investors with a very high tolerance for risk.