Can Casgevy Cure Sickle Cell Disease? 5 Things to Know About This Groundbreaking SCD Treatment

For those who have sickle cell disease (SCD), managing it and avoiding triggers can be a daily grind. After all, pain crises from SCD are severe and can lead to health complications over time.

This inherited (genetic) blood disorder affects as many as 100,000 people in the U.S. And among this group, Black people face an unequal challenge, with approximately 1 in every 365 being born into a lifelong journey with the condition. Finding long-term solutions for SCD has been a goal for decades.

Enter Casgevy (exagamglogene autotemcel, or “exa-cel”), an innovative gene therapy medication that won FDA approval in December 2023. It’s a potentially life-changing SCD treatment for people who qualify. It was also approved for a different condition, called beta thalassemia, in January 2024. But like with any medication, it’s not perfect.

Here are the top five things to know about Casgevy for SCD.

1. Is Casgevy a cure for sickle cell disease?

Yes. Casgevy is a possible cure for SCD in people ages 12 years and older. In a press release, its manufacturers said the medication “offers the potential of a functional cure” for people living with the condition. It aims to eliminate pain crises and hospitalizations from SCD.

This is because Casgevy is a one-dose gene therapy medication. It corrects a genetic problem that causes red blood cells to sickle, or form a hook-like shape.

Gene therapy aside, the only other potential cure for SCD is a bone marrow transplant. It replaces problematic blood stem cells with healthy ones. But this is only an option if you’re able to find a compatible stem cell donor, which can be tricky.

2. How does Casgevy and CRISPR-Cas9 work?

Casgevy edits the genetic makeup of stem cells in your blood. These are early-stage cells that mature into different types of blood cells. Casgevy modifies a gene (a segment of DNA) in these cells so they can develop into red blood cells that contain healthy hemoglobin. Hemoglobin is an important, oxygen-carrying protein that lives inside of your red blood cells.

There’s a lot of detail that goes into this, though. And CRISPR-Cas9 gene editing technology stands at the center of it. Casgevy is the first FDA-approved medication to use CRISPR-Cas9 — a Nobel Prize-winning innovation.

CRISPR-Cas9 and sickle cell disease

CRISPR stands for “Clustered Regularly Interspaced Short Palindromic Repeats.” It’s a strand of RNA (a molecule) that can latch onto a small, but carefully selected patch of DNA in your cells. Cas9 is a protein that cuts into this DNA like a microscopic pair of scissors. Together, they allow scientists to make edits to problematic genes.

With SCD, a gene called BCL11A is in the spotlight. Normally, this gene tells your body to stop making fetal hemoglobin soon after you’re born. This is a specific type of hemoglobin you need while developing in the womb. Your body then begins to make a different form of adult hemoglobin that your body will use instead. This process works well for most people, but this is when issues start to appear for people with SCD. The new hemoglobin that people with SCD begin to make can cause the red blood cells to be stiff and sickle-shaped, rather than soft and round.

With Casgevy, CRISPR-Cas9 finds, cuts into, and turns off BCL11A. This forces your cells to revert back to making fetal hemoglobin. This type of hemoglobin isn’t affected by SCD and won’t get sickle-shaped. More fetal hemoglobin leads to healthier red blood cells and fewer health complications for people with SCD. 

3. How and where can you receive Casgevy?

Casgevy is given as an intravenous (IV) infusion. It’s made using your own stem cells. But because preparing and administering Casgevy can be tricky, you can only receive it at a limited number of sites. Only a handful of authorized treatment centers around the U.S. are able to administer it.

Here’s a step-by-step guide to receiving Casgevy:

1. Schedule an appointment with an authorized Casgevy treatment center. The staff at the treatment center will double-check that you’re a good candidate to receive the medication.

2. Next, you will prepare your body for a process called apheresis, in which your stem cells will be collected. About 2 months prior, you may be told to stop taking your sickle cell maintenance medications. You may also receive blood transfusions during this time to make sure your red blood cell levels remain steady.

3. A few days before apheresis, you’ll receive a medication called Mozobil (plerixafor). This drug pushes your stem cells from your bone marrow to your bloodstream. This will help your care team collect an adequate sample of stem cells. This may take about 3 days.

4. After your stem cells are collected, they’ll be sent to a lab. This is where scientists will use CRISPR-Cas9 to turn them into your dose of Casgevy. Once your dose is ready, the lab will ship it back to your treatment center. This process can take up to 6 months.

5. At this point, you’ll travel back to your treatment center to receive a chemotherapy medication called busulfan. This is done to eliminate your original stem cells, making way for the modified ones to take over. This process may take up to 4 days.

6. Now, you’re ready to receive your Casgevy infusion. The infusion itself should take about an hour.

7. After you receive the infusion, you’ll likely stay in the hospital for a few weeks. This is done for monitoring and safety purposes.

4. Casgevy appears to be safe and effective, but we’re still learning about its long-term effects

The FDA approved Casgevy because its benefits generally outweigh its risks. In a clinical study, over 90% of people who received it didn’t experience any severe pain crises for at least 1 year.

However, researchers are still learning about its long-term effects.

In an interview with GoodRx Health, Lewis Hsu, MD, the chief medical officer of the Sickle Cell Disease Association of America, noted that while Casgevy’s “clinical trials have shown remarkable success in reducing the severe pain of sickle cell disease … getting broad access to this therapy and fully understanding risks and benefits will be the next big tasks to tackle.”

Off-target effects

CRISPR-Cas9 is designed to fix very specific genetic mutations. But in theory, it could accidentally affect other genes by mistake. This is called “off-target” gene editing. Some of these changes could be meaningless, but others could lead to health issues. It all depends on which genes are affected.

There haven’t been any issues with off-target gene editing so far. But since Casgevy's initial clinical trials involved a small number of people over a relatively short period of time, it's possible that issues could appear in the future.

Health experts will keep an eye on Casgevy’s long-term effects, both positive and negative. One long-term study is set to follow people who received Casgevy through 2039. A long-term study like this is the best way to monitor for potential issues with off-target gene editing.

Other side effects

Several side effects were seen during Casgevy’s clinical trials. They may be related to Casgevy, chemotherapy, or both.

Before you receive Casgevy, your treatment team will fill you in on potential side effects you can expect. They may include:

• Mouth sores

• Lower-than-normal appetite

• Stomach pain

• Muscle pain

• Gallstones

• Low blood cell counts

• Infertility (from the busulfan chemotherapy)

• Allergic reactions

5. There may be ways to save on Casgevy

One dose of Casgevy is listed at $2.2 million. This is compared to the average lifetime cost of managing SCD, which one study reports as $1.7 million. Other estimates suggest this number is closer to $4 to $6 million among people who experience recurring pain crises.

There will likely be ways to save on Casgevy, but this will vary on a case-by-case basis. Private and government insurance plans are still deciding if and how they’ll cover Casgevy.

If your healthcare provider wants you to receive Casgevy, the best thing to do is get in touch with a care manager from Vertex Pharmaceuticals — one of Casgevy’s manufacturers. They can talk to you about financial logistics. You can reach them at 1-833-VERTEX-5 (1-833-837-8395). They can also tell you if and when you should contact your insurance company for a coverage appeal.

If you’re still deciding if Casgevy is right for you, you can still reach out to the manufacturer for more information. But if you haven’t received a prescription yet, it may be better to contact a Vertex patient educator through their online portal. They can give you more general information about the medication.

Other medications that treat SCD

Casgevy isn’t the only SCD gene therapy. Lyfgenia (lovotibeglogene autotemcel, or “lovo-cel”) is another option. It has the same treatment goals as Casgevy, but it doesn’t use CRISPR-Cas9 technology.

Many other SCD medications are available, too. These treatments are designed to prevent SCD complications over time:

• Hydroxyurea (Droxia)

• Voxelotor (Oxbryta)

• Crizanlizumab (Adakveo)

• L-glutamine (Endari)

• Penicillin

• Blood transfusions

These treatments offer support when you’re actively experiencing a pain crisis:

• Nonsteroidal anti-inflammatory drugs (NSAIDs), such as ibuprofen (Advil, Motrin)

• Acetaminophen (Tylenol)

• Opioid pain medications, such as hydromorphone (Dilaudid)

• Ketamine infusions

• Supplemental oxygen and/or fluids

• Acute blood transfusions

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Written by:

Joshua Murdock, PharmD, BCBBS

Joshua Murdock, PharmD, BCBBS, is a licensed pharmacist in Arizona, Colorado, and Rhode Island. He has worked in the pharmacy industry for more than 10 years and currently serves as a pharmacy editor for GoodRx.

Reviewed by:

Karla Robinson, MD

Karla Robinson, MD, is a medical editor for GoodRx. She is a licensed, board-certified family physician with almost 20 years of experience in health through varied clinical, administrative, and educational roles.

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