Bill Lundberg, M.D., has stepped down as CSO of CRISPR Therapeutics. News of Lundberg’s departure emerged on the same day Celgene revealed it has sold another chunk of its once-double-digit stake in the CRISPR/Cas9 gene editing startup.

Lundberg landed at CRISPR in 2015 with a brief to lead the establishment of its R&D operation. With the Cambridge, MA facility ticking over and the most advanced candidates developed at the site on the cusp of the clinic, Lundeberg is moving on. Lundberg’s departure is immediate but the ex-Alexion VP will continue to help CRISPR as a senior advisor and as head of its scientific advisory board.

The departure leaves CRISPR without a CSO. In the absence of Lundberg, Tony Ho, M.D., will oversee CRISPR’s R&D activities. CRISPR appointed Ho, who previously worked at AstraZeneca and Merck, as its head of R&D in August. Ho inherits a broad preclinical pipeline of ex vivo and in vivo CRISPR/Cas9 programs CRISPR hopes will quell doubts about whether the technology is ready for prime time. 

CRISPR revealed the change at the top of its R&D organization on the same day as Celgene disclosed it has sold more of the biotech’s stock. Celgene bought 4 million shares in 2015 and acquired more stock in CRISPR’s October 2016 offering to keep its stake above 12%. But the big biotech steadily cut its position in the last two months of 2017, before ending the year with a flurry of stock sales. The selloff resumed this week when Celgene offloaded another sizable tranche of stock.

Celgene’s stake now stands at 6.1%, less than half what it was 16 months ago. Bayer, in contrast, has continued adding to its holding in the biotech. The German company joined with CRISPR late in 2015 for a collaboration that led to the creation of Casebia Therapeutics.

Shares in CRISPR exited after-hours trading flat.