Since the beginning of 2023, equity markets have been experiencing what could be the start of a bull run. Buying shares of growth stocks is an excellent move for investors looking to ride this wave. And while there are plenty of options on the market, looking at the healthcare industry -- where many businesses remain somewhat stable regardless of economic conditions -- could be just what the doctor ordered, considering we are still facing some economic issues.

In that spirit, let's examine two growth stocks in the biotech industry worth investing in today: Sarepta Therapeutics (SRPT 1.38%) and Exelixis (EXEL 1.60%).

1. Sarepta Therapeutics

Sarepta Therapeutics is a biotech company that develops therapies for rare illnesses, especially Duchenne muscular dystrophy (DMD). This progressive genetic disease is accompanied by several symptoms, most notably muscular weakness. Sarepta Therapeutics has developed four treatments for DMD already, but the latest looks the most promising.

On June 22, the biotech announced -- despite a regulatory delay -- that it had received approval from the U.S. Food and Drug Administration (FDA) for Elevidys, a one-time curative treatment for DMD ambulatory pediatric patients between four and five years old. Elevidys addresses the disease at the genetic level.

Sarepta's three other DMD medicines merely ease patients' burdens. For instance, Exondys 51, which is part of Sarepta's arsenal, helps lessen muscle weakness. That's why Elevidys could be a bit of a game-changer. Sarepta Therapeutics' top-line growth has been strong even without it.

In the first quarter, the company's revenue increased by about 20% year over year to $253.5 million, an excellent top-line growth rate for a biotech company. Sarepta Therapeutics estimates peak annual sales of $4 billion for Elevidys, which it co-developed with Roche.

The latter owns the rights to Elevidys outside of the U.S. and will pay royalties to Sarepta Therapeutics, which retains the therapy's commercialization right in the U.S. Still, Elevidys should be a meaningful addition to Sarepta Therapeutics' portfolio and help it grow its revenue even faster. But the biotech isn't stopping yet.

It is still developing new treatments for DMD and is targeting other rare illnesses as well. The company currently boasts more than 40 programs in its pipeline, which is very impressive for a biotech flirting with large-cap territory at a valuation of nearly $10 billion. Sarepta Therapeutics' innovative potential in rare diseases should yield many more approvals in the coming years, leading to consistently solid financial results and stock market performance for the biotech. 

2. Exelixis 

Exelixis is an oncology specialist whose biggest claim to fame is Cabometyx, a treatment it developed for treating some forms of liver and kidney cancer. Cabometyx is the top prescribed tyrosine kinase inhibitor -- a form of targeted therapy -- in renal cell carcinoma (kidney cancer) and second-line hepatocellular carcinoma (liver cancer).

Exelixis has milked Cabometyx for all it is worth and is still doing so. The medicine has earned a slew of new indications that have helped broaden its target market and kept its revenue going in the right direction. In the first quarter, Exelixis' top line of $408.8 million increased by almost 15% year over year. For the entire fiscal year, the biotech projects total revenue between $1.775 billion and $1.875 billion.

At the midpoint, that would represent year-over-year growth of 13.4%. Cabometyx is undergoing more clinical trials and should earn additional approvals over time. But Exelixis is also developing brand new therapies. It is currently running phase 3 studies for zanzalintinib in treating metastatic colorectal (colon and rectal) cancer and advanced kidney cancer.

In both cases, there is a dire need for treatment options once these diseases have metastasized. For instance, the five-year survival rate of colon cancer is 90% when caught at the local stage before it metastasizes. At the distant stage, the five-year survival rate drops to an abysmal 13%. Clearly, there is a strong need here, and Exelixis is looking to fill the gap.

The company has many more programs in early-stage studies that should advance to phase 3 trials within the next couple of years. Exelixis isn't the most popular biotech company around, but its focus on oncology and its proven ability to develop novel therapies in this field make it a reasonable option for long-term investors.