Thomas Hunig, the German professor who founded the TeGenero company, said he still hoped the drug, TGN1412, could be brought to the market.
He said he was devastated that the six men were taken ill but said that he was "not going to give up".
Professor Hunig said: "I do hope TGN1412 can come to the market. This tragic incident does not exclude the theoretical application of TGN1412 some time in the future.
"The company knows that the strategy deserves, in the end, to prevail.
"I don't want to hurt anybody in any way. I don't want to come across as a crazy scientist who wants to save his baby despite the victims he has taken. Definitely not."
But he added: "I am carrying on my projects here - we are not going to give up.
"I owe this not only to myself but also to the many excellent students and colleagues who have done fantastic science.
"At the danger of sounding pathetic, I feel I owe it to the poor guys who have suffered in the TGN1412 trials."
Four of the men are continuing to recover while two remain in a critical condition.