A little more than a year after taking on the role, the CEO of Editas Medicines is preparing to pass the torch, continuing a series of executive changes at the gene editing company.
Effective June 1, Jim Mullen will be replaced by Gilmore O'Neill, who most recently served as the chief medical officer at another company heavily invested in gene therapy research, Sarepta Therapeutics. Mullen isn't cutting ties with Editas, though. He will stay on as executive chairman of the company's board of directors, a position he held before and during his time as CEO.
"Unlike some of the things that we've seen in the past, this is a very mindful, thoughtful transition," said Mullen, in an interview.
Editas hit a major milestone while under Mullen's leadership, producing data from the first clinical trial of a treatment made with CRISPR gene editing technology that works inside the body. Yet Editas, like many of its peers, has also seen its stock price fall significantly over the past year. Though investors have pulled back from the biotechnology sector on a broad scale, the impact has appeared particularly large among genetic medicine developers.
Despite its status as one of the most advanced CRISPR-focused biotechs, departures and arrivals have been fairly commonplace in Editas' top ranks over the past several years. Executives overseeing scientific research, finance and clinical development programs have left. And two months ago, the shake-ups continued with the firing of the company's chief medical officer, Lisa Michaels.
Editas has also had three different CEOs since 2014. Mullen, who took the reins from Cynthia Collins last February, had previously held the same position at Biogen as well as Patheon, the contracted drug manufacturer bought by Thermo Fisher.
Now, Editas plans to have another new chief by June. Like Mullen, O'Neill spent years at Biogen where, in addition to other roles, he served as a senior vice president for late-stage clinical development. More recently, though, he has been in charge of clinical testing, medical and regulatory affairs at Sarepta. According to Editas, O'Neill was integral in the development of medicines like Sarepta's Amondys 45 and Vyondys 53 as well as Biogen's Spinraza, Plegridy and Tecfidera.
Editas also noted that, at Sarepta, O'Neill led the team responsible for discovery research, preclinical testing, clinical testing and global regulatory strategy regarding the company's RNA and gene therapy programs.
"Clearly, one of the things that's been missing from this company is this very experienced, accomplished drug development background that can connect the medicine with the science," Mullen said in an interview with BioPharma Dive. "[O'Neill] is exactly the profile we need at this moment in time."

O'Neill said he weighed several opportunities for his next position but Editas "leapt off the page."
The search for a new chief medical officer to replace Michaels will be one of O'Neill's top priorities following the transition, both he and Mullen said. Executing on research and development as well as exploring business development opportunities will also be high on O'Neill's to-do list.
"The challenge of gene editing and the challenge for Editas is the opportunity [of CRISPR]," said O'Neill. "What we have to do is focus in a pragmatic manner and find ways to balance the bandwidth of an organization and its business partners in actually delivering on these technologies."
Editas currently has 10 programs in its pipeline of gene editing medicines, with the majority not yet in human testing. Of the three programs that have been tested in humans, one targets a rare eye disorder while the other two go after the blood disorders sickle cell disease and beta thalassemia.
Editas' share price was little changed at market's open Thursday. However, it fell more than 8% during morning trading to hover above $17. Editas stock has lost about 58% of its value over the past year.
Ned Pagliarulo contributed reporting.