So far, 2023 is turning out to be a pretty good year for growth stock investors in general. The Vanguard Growth ETF has already gained 19% in 2023.

For investors with either CRISPR Therapeutics (CRSP -1.33%) or Nanox (NNOX -0.51%) in their portfolios, it's already been a great year. Shares of both stocks are way up recently. They've risen for straightforward reasons, but there are a few things you should know before trying to ride their momentum higher.

1. CRISPR Therapeutics

Shares of CRISPR Therapeutics are up more than 57% since the end of 2022. This is still a clinical-stage business that doesn't have any products to sell yet.

Instead of product sales, investors have been cheering for progress with its large pipeline of next-generation therapies. CRISPR Therapeutics' lead candidate, exa-cel, is a gene therapy aimed at treating sickle cell disease and beta-thalassemia patients who require regular blood transfusions.

A single administration of exa-cel should permanently free patients from reliance on problematic blood transfusions. Recently, the company and its collaboration partner, Vertex Pharmaceuticals, finished submitting applications for exa-cel to the U.S. Food and Drug Administration (FDA). The agency has two months following the submissions to announce whether or not it will begin a review process expected to last about eight months.

In clinical trials supporting its application, treatment with exa-cel dramatically reduced patients' dependence on transfusions, and this isn't the only promising candidate in the pipeline. In addition to exa-cel, CRISPR Therapeutics is running trials with four cancer therapy candidates.

2. Nanox

Shares of Nanox have more than tripled since the end of April. That's because on May 1 the FDA granted the company clearance to market its lead product, the Nanox.ARC.

Nanox.ARC is a multisource X-ray system that produces 3D images similar to a CT scan but with a major advantage. Today's CT scanners still rely on X-ray bulbs that heat a filament past 2,000 degrees Celsius (3,632 degrees Fahrenheit) to produce one stream of electrons that rotates around the patient. The Nanox.ARC employs multiple silicon chips that emit controllable electron streams at easy-to-manage temperatures using low voltage.

Traditional X-ray bulbs are so expensive to replace that access to medical imaging is far more limited than it could be. To take advantage of its relatively low cost, the company intends to market Nanox.ARC to heaps of smaller healthcare providers that typically don't have their own 3D imaging capability, such as urgent care clinics.

Good stocks to buy now?

Both of these stocks have a chance to climb much higher, but they may present more risk than you're willing to accept. A pay-per-scan business model could entice many care providers that never imagined being able to produce their own 3D images to install a Nanox.ARC device. Unfortunately, this is a long way from guaranteed.

Given the disastrous launch of the single-source version of Nanox's X-ray machine, investors should probably temper their enthusiasm for the ongoing Nanox.ARC launch. The company's first product received clearance in 2021, but the business is still losing money on every one that it sells.

Nanox's cost of goods sold exceeded revenue by 80% last year, but this company still boasts a $1.1 billion market cap at recent prices. If the Nanox.ARC launch proceeds similarly, investors who buy the stock at recent prices could suffer heavy losses. It's probably best to wait and make sure this Israel-headquartered business can successfully launch a disruptive new medical device in the complicated U.S. market.

When it comes to CRISPR Therapeutics, investors need to realize how hard it is to make money selling a treatment that patients receive just once. The science has come a long way, but this company doesn't have any answers for insurers and government payers that balk at the high upfront costs it will need to charge to realize a profit on sales of once-and-done gene therapies.

Enthusiasm for CRISPR Therapeutics' monumental medical achievements may drive the stock higher, but it's already boasting a $5.0 billion market cap. This is another high flier that is probably best observed from a safe distance until it has a chance to prove itself.