The stock market has performed relatively well since the beginning of the year although, of course, there is no guarantee that it will maintain that momentum. Who knows what curve ball the future has in store for us? Regardless of what happens, investing in market leaders with robust underlying businesses and excellent prospects is still usually a good idea.

Let's consider two such stocks in the biotech industry: Vertex Pharmaceuticals (VRTX 0.35%) and Regeneron Pharmaceuticals (REGN 0.97%). Find out why these drugmakers are worth investing in today.

1. Vertex Pharmaceuticals

Cystic fibrosis (CF) is a rare genetic disease that causes thick mucus that hinders the normal functioning of the lungs, pancreas, and other internal organs. Vertex Pharmaceuticals has developed several medicines that address the underlying causes of CF, the only ones in the world. The biotech's monopoly in this area has famously allowed it to generate growing revenue and profits.

Though Vertex still gets most of its revenue from its CF franchise, things are about to change. The drugmaker recently earned approval for Casgevy, a gene-editing therapy for two rare blood diseases. It developed the treatment with CRISPR Therapeutics. Furthermore, Vertex has made significant clinical progress in recent months. It reported positive results from a phase 3 study for a potential medicine for acute pain called suzetrigine.

Vertex also initiated a rolling submission to the U.S. Food and Drug Administration (FDA) for suzetrigine. Its next-gen CF therapy also aced a late-stage study, and it advanced inaxaplin, an investigational treatment for APOL-1 mediated kidney disease, to the phase 3 portion of a phase 2/3 clinical study.

Vertex's portfolio, which is already driving excellent top-line growth, should be transformed in the next five years. It will provide a solid foundation for the company well beyond that time, especially when we consider Vertex's programs in early-stage trials.

That includes VX-880, a potential functional cure for type 1 diabetes. Last year, Vertex reported that two diabetes patients treated with VX-880 with more than one year of follow-up in a phase 1/2 study had achieved insulin independence. Early results, sure, but highly encouraging ones nonetheless.

More importantly, Vertex's culture is centered around innovation, going after diseases with a high unmet need, and it has been very successful in the past. Vertex Pharmaceuticals should continue delivering superior returns for a long time. That's why the stock is a buy right now -- and one of the most attractive ones in the biotech industry.

2. Regeneron Pharmaceuticals

Regeneron Pharmaceuticals is another highly innovative biotech with several growth drivers in its arsenal. Admittedly, the company's financial results didn't impress in the first quarter. Revenue declined by 1% year over year to $3.1 billion. However, the drugmaker was active in the coronavirus therapy market, which is now shrinking rapidly. Excluding sales from its COVID-19 antibody, revenue increased 7%.

One of Regeneron's key growth drivers is cancer medicine Libtayo. In the first quarter, revenue from this product came in at $264 million, 45% higher than the year-ago period. The biotech's current biggest growth driver, though, is Dupixent, a medicine for eczema. Regeneron co-markets Dupixent with Sanofi. The drug's global sales in the first quarter (recorded by Sanofi) came in at $3.1 billion, up 24% year over year.

Dupixent is currently racing toward an important label expansion in treating COPD. The medicine's peak sales could exceed $20 billion by the end of the decade, with the COPD approval contributing roughly $3.5 billion of that total, according to some estimates. For reference, Dupixent's sales were $11.59 billion last year.

Regeneron's second-most-important product, Eylea, is at a critical point. Eylea is a medicine for wet age-related macular degeneration co-marketed with Bayer. In August of last year, the partners earned approval for a high-dose formulation of the drug that is just as effective but with fewer annual doses.

In the first quarter, Eylea and Eylea HD's combined global sales were $1.4 billion, a decrease of 2% compared to Eylea's global sales in Q1 of 2023. However, as Eylea HD gains traction, things should start moving in the right direction again. After all, it's only been on the market for two full quarters.

Meanwhile, Regeneron has plenty of exciting pipeline candidates, especially in oncology. The company's financial results will improve substantially compared to what we saw in the first half as Regeneron moves beyond coronavirus-related dynamics; Eylea, Dupixent, and Libtayo contribute to top-line growth; and the biotech earns approval for brand-new products. Strong stock performance should follow.