It was a heck of a year for bluebird bio (NASDAQ:BLUE), with shares more than tripling in 2017, although they pulled back a little in December; the biotech ended the year up only 188.7%.

BLUE Chart

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As the chart shows, the stock price benefited from three large jumps in June, August, and December. Here's how it went down.

June: ASCO abundance

In June, at the annual American Society of Clinical Oncology (ASCO) meeting, Bluebird and its partner Celgene (NASDAQ:CELG) presented data from the first 15 multiple myeloma patients treated with bb2121 at the highest three doses. While it was a small number of patients, investors were rightfully impressed by the 100% response rate, especially given that the patients had been treated with a median of seven prior therapies.

bb2121 is part of a new class of therapies called chimeric antigen receptor T-cell (CAR-T) therapies that take immune cells out of patients, train them to attack cells expressing a certain protein -- B-cell maturation antigen (BCMA) in the case of bb2121 -- and put them back into the patient to do their job.

August: Gilead buys Kite

At the end of August, it wasn't so much anything that Bluebird did, but that Gilead Sciences (NASDAQ:GILD) acquired fellow CAR-T drugmaker Kite Pharma for $11.9 billion. Kite's lead drug doesn't compete with bb2121, so the acquisition shouldn't have an immediate effect on Bluebird. Long term, though, investors should keep an eye on KITE-585, a BCMA CAR-T therapy that entered phase 1 development in August, which Gilead also got as part of the deal.

Despite the potential competition from a larger rival, investors saw Gilead's purchase as an endorsement of CAR-T therapy and Bluebird as a potential takeout target. It's arguable whether either of those really made Bluebird more valuable since Bluebird already had an endorsement from Celgene, which would be the most likely suitor. But long-term investors will take the stock price jump nonetheless.

Doctor talking to patient in exam room

Image source: Getty Images.

December: Another ASH

In December, Bluebird and Celgene presented more data on bb2121 at the American Society of Hematology (ASH) meeting. The objective response rate dipped to 94%, but with the number of patients having grown to 18 and longer-term data available, investors were feeling more confident that the treatment really is working. Importantly, 56% of the patients had a complete response, with 90% of those having reached a level where the disease was undetectable.

Again, these are pretty impressive numbers considering how sick the multiple myeloma patients in the trial were, given their minimum of three prior therapies and a median of seven prior therapies. For context, Johnson & Johnson's Darzalex was initially approved for patients who received at least three prior lines of therapy based on a 29% overall response rate and a 3% complete response rate.

All year long

While bb2121 arguably stole the show for 2017, Bluebird's LentiGlobin gene therapy program shouldn't be overlooked. The program spent most of the year recovering from a disastrous 2016, when its LentiGlobin program didn't live up to high expectations found in the first few patients. Bluebird went back to the drawing board and increased the number of copies of the gene that are expressed in each cell, which appears to have helped.

In data presented at ASH, the first two sickle cell patients treated with the new manufacturing protocol had 51% and 28% expression of anti-sickling HbAT87Q at six and nine months, respectively, which is higher than had previously been seen using the old manufacturing protocol.

Looking ahead

It'll likely be hard for Bluebird to match its stellar 2017 this year, as much of the data will just be confirmation of previously released clinical trial data.

In September, Bluebird and Celgene started an expansion cohort of patients to identify the best dose of bb2121. Initial data for those patients will presumably be available sometime this year, as will additional data for sickle cell patients treated with LentiGlobin.

LentiGlobin can also treat another blood disease called transfusion-dependent beta-thalassemia, which has helped patients no longer require chronic transfusions. In November, management indicated that it'll release a timeline for filing marketing applications for that disease this year.

Editor's note: A previous version of this article stated that Kite Pharma was acquired for $11.9 million instead of $11.9 billion. The Fool regrets the error.

Brian Orelli has no position in any of the stocks mentioned. The Motley Fool owns shares of and recommends Bluebird Bio, Celgene, Gilead Sciences, and Johnson & Johnson. The Motley Fool has a disclosure policy.