ZURICH (Reuters) - Swiss drugmaker Roche said it will put a cancer specialist at the helm of its Swiss-based research efforts in April, after the scientist who led the unit for five years resigned for personal reasons.

FILE PHOTO: Roche tablets are seen positioned in front of a displayed Roche logo in this January 22, 2016 file illustration photo. REUTERS/Dado Ruvic/Illustration/File Photo/File Photo

The biggest maker of cancer drugs named William Pao to lead its 2,200-employee Pharma Research and Early Development (pRED) unit on Thursday.

Current postholder Reed, 59, arrived in Basel in 2013 to rebuild Roche’s Swiss research after restructuring. He plans to return to the United States.

Pao now heads pRED’s oncology discovery and translational area and will assume his new role on April 2, Roche said in a statement.

Roche has been touting prospective drugs from its long-underperforming Swiss-led research unit after years of leaning on its California-based Genentech arm for all of its blockbusters.

While pRED’s drug hopefuls including autism and blood cancer agents have advanced under Reed to late-stage studies, planned filings for approval are still at least a year away.

“I am thankful to have had John Reed with Roche over the past five years, and for all his many valuable contributions,” Chief Executive Severin Schwan said. He added Pao had been instrumental since coming to Roche in 2014 in building out cancer immunotherapy and molecular targeted therapies.

Before joining Roche, Reed, an expert in why cells die, did a 21-year stint at Sanford-Burnham Medical Research Institute in San Diego, California -- far from Roche’s campus near the Rhine River at the Swiss, French and German borders.

Pao, who will be based in Basel, joined Roche in 2014 from the Vanderbilt University Medical Center in Nashville, Tennessee.

Under Reed, he has overseen pRED’s list of oncology hopefuls including CEA-TCB, a so-called bispecific antibody drug that brings a patient’s cancer-fighting T-cells closer to tumour cells to kill them.

Pao is also co-founder of MyCancerGenome, an online tool to enable a genetically informed approach to cancer medicine.

“William has been instrumental in the build-up of cancer immunotherapy and molecular targeted therapies,” said Schwan.