(Reuters) – Bluebird bio slumped nearly 13% on Thursday on concerns over a limited patient pool for its newly approved $2.8 million gene therapy, which investors are hoping can help pull the small drugmaker out of a cash crunch.

Zynteglo – which was approved by the U.S. Food and Drug Administration on Wednesday for patients with beta-thalassemia requiring regular blood transfusions – is being priced at a record $2.8 million, making it the most expensive therapy to date.

Despite its price tag, analyst don’t foresee the drug becoming a major revenue driver for the company as the addressable patient population is very small and not many patients may be willing to undergo this treatment.

“Don’t expect blockbuster sales from Zynteglo,” Oppenheimer Company analyst Mark Breidenbach said.

There are an estimated 1,500 beta-thalassemia patients who require regular transfusion in the United States.

Founded in 2010, bluebird has been riddled with challenges in the past few months, pulling Zynteglo from Europe in a dispute over pricing and cutting 30% of its workforce. In March, the company also flagged “going concern” doubts.

(Reporting by Mrinalika Roy in Bengaluru; Editing by Anil D’Silva)