Clay Siegall is proud of his legacy as co-founder and longtime CEO of Seagen, the largest biotech company in the Seattle area.
“I built a great company,” Siegall said in an exclusive interview with GeekWire on Wednesday.
He co-founded the company then known as Seattle Genetics in 1997, helped bring it public in 2001 and oversaw the approval of four oncology drugs.
Last week, Bothell, Wash.-based Seagen announced plans to sell to Pfizer for $43 billion, the biggest biopharma acquisition in three years.
But Siegall, who had led the company since 2003, was not in charge as the deal came together.
He resigned as CEO and chairman of Seagen in May following an alleged domestic violence incident at his home involving his then-wife. Prosecutors said in December they would not press charges, citing inconsistent and contradictory statements about the incident, the Seattle Times reported. Siegall and his wife finalized their divorce in October.
Siegall is now back in biotech, with Wednesday’s announcement that he is CEO and president of Morphimmune, a Purdue University spinout with expansion plans in Seattle.
Finding new ways to treat cancer has been Siegall’s focus since his father was diagnosed with a lethal brain tumor when Siegall was 19. He said his biggest source of pride from the Seagen journey is the therapies the company developed.
“It’s not the money that’s most important, it’s the lives that are saved,” said Siegall, who was the largest individual Seagen shareholder as of Dec. 31. Siegall earned $18.9 million in total compensation in 2021.
Seagen helped pioneer the development of a class of drugs called antibody-drug conjugates (ADCs), which recognize a target on cells via an antibody and deliver a toxin or other active payload.
Siegall said he was laughed out of the room by some venture capital firms when he tried to raise money for the company in its early days.
Now there are 12 approved ADCs and dozens of companies developing new ones. Seagen employs 3,300 people across the world and reported $2 billion in revenue last year.
“I think one of my best characteristics is I have a strong backbone, and I’m persistent,” Siegall said. “And I really, really care about cancer patients.”
Read on for more from our conversation with Siegall. Questions and answers were edited for brevity and clarity.
On the pending Pfizer acquisition
“That one of the biggest pharmaceutical companies in the world, Pfizer, is buying into this is fantastic. It shows that ADCs have come of age. That the work I did to help so many patients is now going to be done and led by one of the greatest pharmaceutical companies on the planet — I can’t be more proud.”
On rebuffing earlier acquisition attempts
“There were definitely times when companies were trying to acquire Seagen, when we were Seattle Genetics. But each time that we looked into it, when we were small and growing, we thought we had a lot of trajectory.
I brought it to the board each time. I was really a proponent that we could grow this company, and the board would ask things like, ‘What’s your vision to grow this?’ And I would say, ‘Here’s my vision to grow it from a $500 million company to a $3 billion company to a $5 billion company.’ It didn’t seem logical to sell the company at that point since the growth rate was so logarithmic. And that happened for 20 years.”
On whether it was strange to see the Pfizer acquisition announcement after resigning
“When you are at the same place for 25 years, yes, there is a little strangeness to it. But you know what, it’s OK. And I’m totally delighted with this new enterprise I have. And I’m going to do it again.”
On a key lesson learned about building a company
“I would say that the most limiting quantity is time — money is not. You can get money to build companies.
It’s a matter of price. I don’t know any company that ever went bankrupt from dilution. Sometimes it’s okay to sell some stock in a company maybe a little bit lower than you want to, to get the quality investor in.
Allowing investors to make some money on what you’re doing is a good thing, because they’ll come back and invest in the next round and in the next round. Biotech is a cash-intensive business. I always have the long view.”
On making the drugs work
“At the time, everyone pooh-poohed ADCs. They weren’t working. And I went back and asked, ‘What is wrong with ADCs?’
The linkers [which connect the antibody and the toxin payload] were wrong, they were difficult. People were using natural products for payloads. I said I wanted to use synthetic drugs for payloads and really good linkers that were stable in the bloodstream but released a drug inside of the tumor.”
On the development of the company’s first drug, the lymphoma treatment Adcetris, approved in 2011
“Most people said the market was not big enough. I also was told that there were good treatments for Hodgkin lymphoma, and we didn’t need any replacements. But I didn’t think that was true, and I thought I could do better. Now, Adcetris is standard of care that has increased the cure rate and decreased many of the toxicities of previous therapies. It’s used in 77 countries, and I’m incredibly proud of it and the work that I did with my colleagues at Seagen.”
