What happened

Despite its Friday lurch downwards, the stock market generally had a good week. Not every company on the exchange did well, however, and that list includes Bluebird Bio (BLUE -2.24%). The gene-editing specialist's shares fell more than 11% earthward, according to S&P Global Market Intelligence, as some pundits got more bearish after the company won regulatory approval for a new drug.

So what

On Wednesday, Bluebird announced it had secured Food and Drug Administration (FDA) approval for its Zynteglo, a drug that targets transfusion-dependent beta-thalassemia (TDT), a rare blood-related disease. Zynteglo is a one-time, gene-based therapy designed to attack the underlying genetic cause of the disorder in both adults and younger patients. It is the first such medication for TDT.

According to Bluebird, around 1,300 to 1,500 people in the U.S. currently suffer from the disease. The biotech said that "due to the complex nature of gene therapy," Zynteglo will only be administered at qualified treatment centers with expertise in gene therapy, among other relevant procedures.

Now what

While any FDA approval is a clear victory for an aspiring biotech, some analysts don't feel Bluebird's newly approved drug will be much of a game-changer.

In a new research report, Oppenheimer analyst Mark Breidenbach wrote bluntly, "Don't expect blockbuster sales from Zynteglo." According to him, only around 850 people in the U.S. with TDT are eligible for treatment with the drug.

Wedbush's David Nierengarten broadly agreed, stating that Zynteglo isn't likely to produce piles of revenue for its developer. He has a more pessimistic view than Breidenbach, anticipating that 50 patients annually, at the most, might choose it as a therapy.

Yet, not every analyst's take was entirely bearish. Goldman Sachs prognosticator Salveen Richter upped her price target on the stock a full 50%; it's now $3 per share from the previous $2. However, Richter is maintaining her sell recommendation.