In order to generate a more consistent and precise insertion, Bluebird developed LentiGlobin with a different viral vector. The belief is that this new version of the drug will both decrease the risks of off-target gene insertion while mimicking (if not increasing) the efficacy. That being said, this new vector has not been dosed in humans and the IPO money will be used for a phase I/II trial. Aside from the Lenti family of drugs, Bluebird also has a preclinical program in chimeric antigen receptor T-cells. The goal is to modify the T-cells to target specific cancer cells and re-infuse them back into the patient. There was some excitement generating at the recent American Society of Clinical Oncology meeting about other CAR T trials but the Bluebird Bio program remains preclinical with no data from use in humans. So the question remains: What to make of the Bluebird IPO? Gene therapy has been around for awhile with limited success (Sangamo continues to struggle with its technology) because delivering genes into cells remains a challenge. Bluebird believes it has addressed this issue with their lentiviral vectors but we have limited clinical data to assess this claim. This both increases the risk as well as the potential rewards. Of course, Bluebird also has its earlier program in CAR T, which is a hot area in oncology drug development. Celgene ( CELG) has taken an interest in Bluebird's work and signed on as a partner and investor. Given the lack of clinical data across the pipeline, the Celgene partnership is an important validation of Bluebird and its technology. Even successful, large-cap biotech companies make mistakes but Celgene's involvement with Bluebird de-risks the CART program by providing not just the validation but a source of non-dilutive capital. While the gene therapy aspect of Bluebird is interesting and will likely provide the nearest term catalysts, I think investors will be just as (if not more) interested in the CAR T program as this will be the only publicly traded company working in the area. All of that being said, investors need to be careful and recognize the increased risks associated with a company that has such limited clinical data on their pipeline. Sobek is long Celgene.