BOSTON (TheStreet) -- In this week's Biotech Stock Mailbag, Ron D. emails, "Do you expect Bluebird Bio (BLUE) - Get Report to have the same positive results in sickle cell disease that they had with beta-thalassemia? When will the company tell us about its sickle cell patients and is there a way for ordinary investors to figure out what is good or not?"

I do expect Bluebird's gene therapy to benefit sickle cell disease patients based on the impressive data (transfusion independence) in beta thalassemia presented last December. Bluebird shares are up almost 60% since December, so it's fair to say a lot of investors share my optimism for positive sickle cell disease data.

Bluebird has not yet disclosed when the sickle cell data will be presented, although speculation centers on the European Hematology Association (EHA) meeting in June as a possible venue. Research abstracts for the EHA meeting will be made public on May 21.

Sickle cell disease is an inherited disorder in which a mutated gene produces misshapen red blood cells. The disease gets its name because the deformed red blood cells looks like sickles or crescents. Healthy red blood cells -- made up of the protein hemoglobin which carries oxygen throughout the body -- resemble oval donuts without a hole in the center. They're flexible and move easily through the body. Sickled red blood cells contain abnormal hemoglobin that is inflexible and sticky. Sickled red blood cells don't carry oxygen well and clump together in blood vessels, causing extreme pain and organ damage.

Like with beta thalassemia, a related blood disease, the goal of Bluebird's LentiGlobin gene therapy in sickle cell disease is to replace the defective gene with one that is normal, thereby restoring the patient's ability to produce properly shaped and functional red blood cells and hemoglobin. Importantly, this is a one-time treatment which is potentially curative.

Today, sickle cell patients undergo regular transfusions of healthy red blood cells in order to dilute the amount of sickled hemoglobin relative to normal hemoglobin. A single drug, hydroxyurea, is also currently approved to treat sickle cell disease. Neither red blood cell transfusions nor hydroxyurea are a cure for sickle cell, but they do improve the disease's primary clinical symptoms -- anemia and painful vaso-occlusive "crises."

Bluebird would like its LentiGlobin gene therapy to cure sickle cell disease. That's a big goal, but to achieve it doesn't necessarily require the production of 100% normally functioning hemoglobin. What's known from studies of sickle cell patients is that a ratio of 60% to 70% normal hemoglobin to 30% to 40% sickled hemoglobin is enough to quell or eliminate symptoms.

Last December, Bluebird showed the proportion of "marked" beta globin, a measure of functional hemoglobin produced by the working gene inserted by LentiGlobin, ranged from 44% to 72% of total hemoglobin in the four beta thalassemia patients. These levels of functional hemoglobin were sufficient to free the patients from requiring blood transfusions.

If these results can be replicated in sickle cell patients, Bluebird says its gene therapy has a shot at being an effective treatment, possibly a cure, for sickle cell disease.

The proof, of course, will come from the actual data in sickle cell patients later this year, so we wait. Bluebird and its gene therapy remain a very exciting biotech story.

Boston Business Journal's Don Seiffert says five companies may be interested in buying Ariad Pharmaceuticals (ARIA) . The article prompted Pelion to ask me, "I know you think (and I agree) Seiffert's list of companies is BS. But how do you view Ariad not publicly responding to allegations in Sarissa's filing?"

Ariad has long been the subject of questionable takeover rumors. None have proven true. Sieffert's list of "new" Ariad suitors -- Roche (RHHBY) , Celgene (CELG) - Get Report, Gilead Sciences (GILD) - Get Report, Amgen (AMGN) - Get Report and Pfizer (PFE) - Get Report -- seems equally implausible.

Seiffert: "Investors with whom I've communicated confidentially suggest there may be an existing bid from Roche on the table, and that Celgene was a bidder a few years back who may now be looking to revisit the opportunity."

Hmmm.... Roche and its Genentech arm develop a vast majority of their cancer drugs in house. When the company does reach outside its own labs, it's almost always to license or acquire cutting-edge technology. Ariad sells a leukemia drug (Iclusig) with limited efficacy due to a worrisome safety profile. A competing leukemia drug is going generic soon. Ariad's lead pipeline drug, brigatinib, is a me-too ALK inhibitor for a small subset of lung cancer patients that might be the third or fourth drug in its class to reach the market.

There's nothing at Ariad compelling enough to garner interest from Roche. I suspect the same goes for the rest of the companies on Sieffert's list. Ariad wouldn't be an expensive acquisition for these large, profitable and cash-rich companies, but it wouldn't budge the revenue meter much either. Successful companies tend not to make inconsequential or financially meaningless acquisitions.

Activist investor Alex Denner of Sarissa Capital is agitating for change at Ariad, including the ouster of CEO Harvey Berger. Ariad hasn't yet responded publicly to Denner's allegations, which Seiffert suggests might mean the company is soliciting takeover bids. Perhaps he's right, or it might mean Ariad is in active negotiations with Denner/Sarissa to reach agreement on changes in the makeup of the company's board -- including Berger's role as CEO.

While I call BS on Seiffert's Ariad suitors list, a sale of the company can't be ruled out. Japanese drug companies have shown interest in mediocre U.S. biotech assets. On Twitter this week, I suggested Germany's Merck KGaA might want to buy Ariad because its existing cancer drug franchise has languished and needs help. Someone else on Twitter suggested Valeant Pharmaceuticals (VRX) , which bought Dendreon and its prostate cancer vaccine Provenge in a bankruptcy sale.

Price is an issue. At an enterprise value of $1.4 billion, any company buying Ariad is paying 10 times expected Iclusig sales of $140 million this year. That's not cheap, especially if you assume Ariad won't agree to a sale without a takeout premium. Throwing Ariad's pipeline into the deal mix doesn't really make it any more attractive from a financial standpoint.

Consider Valeant paid $495 million for Dendreon, which included Provenge ($300 million in 2014 sales) and $80 million in cash.

I try not to answer a question with a question, but here's my thought about the XBiotech (XBIT) - Get Report initial public offering in a week in which Aduro Biotech's (ADRO) - Get Report red-hot IPO garnered much more buzz.

I'll go with the XBiotech IPO as a more troubling sign of a biotech bubble. In a more rational investment climate, XBiotech wouldn't find a public market for its shares. XBiotech's S-1 is filled with classic biotech red flags, including lack of quality venture capital backers, D-list underwriters and dubious clinical data generated from small subsets of patients presented in ways which overestimate treatment effect.

My friend and fellow biotech Twitter tribe member @Zbiotech summed up XBiotech best:

Adam Feuerstein writes regularly for TheStreet. In keeping with company editorial policy, he doesn't own or short individual stocks, although he owns stock in TheStreet. He also doesn't invest in hedge funds or other private investment partnerships. Feuerstein appreciates your feedback; click here to send him an email.