Daniel L. Doctoroff watched in pain as his father developed a limp one day, was found to have Lou Gehrig’s disease, and died within two years. Then an uncle also developed symptoms of the same disease, and died soon after.

Now Mr. Doctoroff, like many other relatives of Lou Gehrig’s disease victims, worries that he or his children may someday develop the illness.

But unlike many, he is in a position to try to do something about it. At a time when scientists are making rapid gains in the genetic roots of many diseases, Mr. Doctoroff, a former deputy mayor and private equity investor, is working with Mayor Michael R. Bloomberg and a private equity director, David M. Rubenstein, to put together a $25 million package of donations to support research to try to cure this rare and usually fatal degenerative neurological illness.

“This is a devastating disease,” Mr. Doctoroff said in an interview this week in the glass high-rise on the Upper East Side that houses Bloomberg L.P., the mayor’s media and financial information company, where Mr. Doctoroff is now chief executive. “Up to now, there’s been basically no hope. I have the resources, and I think it’s my obligation to do that.”