On Friday, the FDA achieved a historic milestone when it approved two one-shot cell-based gene therapies, namely Casgevy (exa-cel) and Lyfgenia (lovo-cel), for treating sickle cell disease (SCD) in patients aged 12 years and older.

Lyfgenia has been developed by bluebird bio (BLUE Quick QuoteBLUE - Free Report) , while Casgevy has been developed by CRISPR Therapeutics (CRSP Quick QuoteCRSP - Free Report) in partnership with Vertex Pharmaceuticals (VRTX Quick QuoteVRTX - Free Report) .

Among the two gene therapies, the approval of Casgevy was more impressive since it marks the first time that the FDA approved a gene therapy utilizing the Nobel prize-winning CRISPR technology. This technology can selectively delete, modify or correct a disease-causing abnormality in a specific DNA segment. Per the FDA, the Casgevy approval marks an important “innovative advancement” in the world of gene therapies. Lyfgenia uses a lentiviral vector (gene delivery vehicle) for genetic modifications.

A rare blood disorder, SCD is a condition marked by a mutation in hemoglobin, which causes red blood cells to develop a crescent or ‘sickle’ shape. These cells impair the ability of red blood cells to deliver oxygen to the body’s tissues, thereby leading to severe pain and organ damage called vaso-occlusive events (VOEs) or vaso-occlusive crises (VOCs). Prior to the Casgevy and Lyfgenia approvals, the only longer-term treatment for SCD was a bone marrow transplant that requires matching donors.

The FDA approvals are based on positive data from the companies’ clinical studies, wherein treatment with both therapies have helped reduce painful episodes in SCD patients.

Despite the positive news, the share prices of all three companies were down on Friday after the FDA’s announcement. While bluebird’s stock plunged 40.5%, both CRISPR and Vertex lost 8.1% and 1.1%, respectively.

This was likely due to the conditions required to be fulfilled to become eligible for treatment with either of the gene therapies. Both Casgevy and Lyfgenia utilize a patient’s blood stem cells, which are modified and then infused as one-time single-shot treatment as part of a hematopoietic (blood) stem cell transplant. This process of collecting stem cells requires the use of high-dose chemotherapy, and such modifying stem cells can take up to six months alone.

In addition to time, both gene therapies have been priced high. In an SEC filing, Vertex and CRISPR disclosed that they would commercially launch Casgevy at $2.1 million. In a separate press release, bluebird announced that it will launch Lyfgenia at $3.1 million.

Despite overcoming the time and price stipulations, treatment with either the CRISPR/Vertex or bluebird gene therapies also has its fair share of side effects, which include low levels of platelets, white blood cells and fertility problems.

Lyfgenia label also includes a black box warning for hematologic malignancy (blood cancer). Patients infused with the bluebird therapy are required to be monitored for this malignancy for life. This was one of the major reasons for the significant decline of bluebird bio’s stock.

Despite the above points, each therapy has an equal opportunity to exploit the market. While bluebird’s gene therapy comes at a higher price point and also carries a black box warning, bluebird bio’s experience with marketing other gene therapies gives it a significant advantage over Vertex/CRISPR.

Currently, bluebird markets Zynteglo for beta-thalassemia and Skysona for active cerebral adrenoleukodystrophy, both of which received FDA approval last year. Casgevy is Vertex’s first approved therapy outside of its marketed portfolio of cystic fibrosis drugs and its first-ever FDA approved therapy for CRISPR Therapeutics.

The FDA is also reviewing Casgevy as a potential treatment for transfusion-dependent beta thalassemia, with a final decision expected by Mar 30, 2024.