If you're looking to add some growth to your portfolio, you may find it in biotech stocks. Two in particular offer investors a terrific opportunity right now. That's because both of them are in the early stages of their growth story. And this means early investors could benefit from these stocks for quite some time.

I'm talking about Axsome Therapeutics (AXSM -0.04%) and CRISPR Therapeutics (CRSP -0.76%). Axsome launched its first two products last year -- and may have more on the way. CRISPR recently requested regulatory approval for a product candidate with blockbuster potential. Which of these innovative biotechs makes the better buy right now? Let's find out.

The case for Axsome

Axsome bought the sleep disorder drug Sunosi from Jazz Pharmaceuticals and started selling it last spring. The company launched a product from its own pipeline -- antidepressant Auvelity -- soon afterward. Both drugs are expected to bring in peak revenue of more than $1 billion.

But Axsome may just be getting started when it comes to growth. The company has five candidates in the pipeline. And each one is in phase 2 development or farther along.

Of course, failure can happen at any point in development -- but risk does decline as a candidate makes it through the earliest safety and efficacy tests. So that's one positive point about having an advanced pipeline. The second positive point is potential products may not be too far off. And products equal revenue.

Axsome has two candidates that may be the next to join its portfolio of commercialized products. The company aims to resubmit its migraine candidate to regulators this year after addressing certain questions. There's reason to be optimistic moving forward. Axsome also reported positive data from a phase 3 trial of its candidate for Alzheimer's disease agitation.

All of this means Axsome may have plenty of revenue drivers over the coming years. And that should lead the shares higher.

The case for CRISPR

CRISPR and partner Vertex Pharmaceuticals recently completed regulatory submissions for exa-cel, their blood-disorders candidate in the U.S., Europe, and the U.K. This is a big deal for CRISPR for two reasons.

First, approval would represent a vote of confidence in CRISPR's gene-editing technology. Exa-cel and other products in CRISPR's pipeline are based on this technology. Second, exa-cel could generate blockbuster revenue. The candidate is designed as a one-time curative treatment for blood disorders beta thalassemia and sickle cell disease. Today, treatment options are limited for these illnesses.

So approval would be a major step forward for CRISPR. And exa-cel offers opportunities for revenue growth down the road -- for example, expanding its indication into children. The companies are testing it in phase 3 trials in kids right now.

The company isn't depending on exa-cel alone, however. CRISPR has many other candidates in the pipeline. One, in particular, is getting closer to the finish line. CTX-110, an immuno-oncology candidate, is in a phase 2 study that could support a regulatory submission.

Finally, CRISPR also generates revenue by licensing its technology to others. Vertex recently signed a deal to use CRISPR's gene editing in its type 1 diabetes program.

All of this makes CRISPR a top growth stock to consider.

Axsome or CRISPR?

You may already be thinking what I'm thinking. It's going to be hard to choose between these two. Let's take a look at the stock price of each to help us along.

Axsome shares soared about 100% last year. But they've given back some of those gains, declining 17% this year. That makes them a great stock to buy on the dip.

CRISPR stock has climbed in recent years -- reaching a record high in 2021. But since that point, the shares have slipped. At the same time, CRISPR's offering more visibility to investors than it ever has before.

I think Axsome and CRISPR both could climb over the long term. And today, they make good buys. But considering CRISPR's declines over the past couple of years and the potential growth ahead, the stock looks exceptionally cheap. That's why it's the top growth stock to get in on right away.