Transcript for How the Ice Bucket Challenge may have helped save future ALS patients: Part 2
led by Lou Gehrig -- Reporter: With the crack of a bat the legendary slugger Lou Gehrig could send a stadium to its feet. But at the height of his career, he was stricken with A.L.S. Today I consider myself the luckiest man on the face of the Earth. Reporter: It became known as Lou Gehrig's disease. But the griming pronot ING pin ING ping proknowles for patients hadn't changed much for 75 years. What they told every A.L.S. Patient is, go home, get your affairs in order, and make that person comfortable for the rest of their life. Pete basically said, "F" that. Reporter: Instead of disappearing into the shadows, Pete Frates was determined to show the world how devastating A.L.S. Really is. Pete now breathes through a ventilator which keeps him alive. It's a difficult decision. Only 10 percent of A.L.S. Patients choose to make it. As a result, a nurse is on hand 24/7. Daily life is a constant and costly struggle. The medical bills around $90,000 a month. Pete's family now fund-raising to help pay those bills. Just a few months ago, his family thought they might lose him. But then after yet another change in medication, Pete battled back. Posting this video. Yes, that's pearl jam's "Alive." Showing that his steely determination and his sense of humor still very much intact. Then again, Pete has a lot to live for. I can't imagine how happy I'm going to be when I have my own little baby. Reporter: This was one of the last times he was able to speak, just before his daughter Lucy was born. Tell me about what you see in his love for his daughter. It's pretty crazy. He's so madly in love with her. She's the light of our lives. What do you tell your daughter about the future? She's never known Pete in another state. Pete's always been in a wheelchair. He's never spoken to her with his voice. He's never picked her up. So this is dad, to Lucy. Lucy, daddy loves you. Reporter: This is how Pete talks to his now 3-year-old daughter. He'll type messages to us on this. Reporter: A tablet screen, now the window to his mind. And right now, he's trying to capture our attention. Oh, that's so cool. This is from the green monster. Oh, boy. Reporter: It's that home run he hit at Fenway park. One of his fondest memories. Just 11 years ago. That is a thing of beauty. Reporter: His story inspiring this book by Casey Sherman. He realized immediately, before anybody did, that this was his mission, this was his purpose in life, was to be the face of this dreaded disease and find a cure for it. I think that is for sure what the ice bucket campaign did. It brought in all these great biologists, engineers, people who never thought about A.L.S., into the A.L.S. Field. Reporter: The ice bucket fund-raising helped usher in medical breakthroughs, from finding an A.L.S. Gene to fast tracking approvals for new drugs and pushing even more into clinical trials. Pete said to us, everything that we do is probably not going to be in time for me, but it's going to be in time so other people will never have to have this happen to them. Reporter: 3,000 miles from Boston, 22-year-old oziel Mendoza is one of the countless patients who's about to benefit from one of those new drugs. Tell me about the impact your doctors are telling you it's going to have on your progression. So it's supposed to slow the disease down by about 33%. So it's the most significant thing that's ever been tested and proven. Reporter: Like Pete, he's an all-around athlete, a team captain, fell in love with his middle school sweetheart Bella. They long dreamed of a beautiful wedding and starting a life together. Just last summer he started to notice a twitching and muscle weakness after a series of tests, the dreaded diagnosis, A.L.S. What was that like getting that news? Still hard to put into words. We never expected to hear that. In our entire lives to hear two to five years is the average years that someone lives after being diagnosed with A.L.S. My whole entire life flashed by me. This is a brace to help you walk? Yes and I wear them on both legs. Reporter: Less than a year after diagnosis he has to use braces to walk. When his right hand became too weak he learned to write with his left. If you could talk to Pete it's right now what would you say to him? First I'd say thank you for everything that he's done. And for the inspiration that he's given me. And many other people with A.L.S. You know, that there's hope. Reporter: That hope means everything. Just three days before oziel's diagnosis, he asked Bella to marry him. Everybody knows the line in the wedding, the wedding vows, in sickness and in health. I'm going to mean it. Because every single day, I try to tell you that I'm never going to leave your side. And I'm not going to. I'm in this until the end. Did you ever discuss not going through with the engagement? It sped everything up a little bit after hearing the diagnosis and what this disease holds. I want to be able to walk down the aisle. I want to be able to go on a honeymoon adventure with her, do things we've always dreamed of. Reporter: And on a picturesque September day, just a few weeks ago, that dream came true. During their vows, he leans on her for support. R worse, for richer or poorer, in sickness and in health -- Mr. And Mrs. Osiel Mendoza. Reporter: A.L.S. Makes it hard to stand for long but osiel is determined to walk his new bride down the aisle, just like Pete Frates did. ??? Someday ??? Reporter: Together they share the first dance of the rest of their lives. ??? When I'm awfully low ??? Reporter: A graceful act of defiance against a disease that steals just about everything. Osiel is 22, Bella is 21. What advice would you give them? If you try and look at the bigger picture, it's almost -- it's just too scary. Every day has to be a day where you just face the challenge that the day holds. Reporter: Back in Boston, Pete and Julie continue to fight for every day. For love. This is Lucy's favorite show. Reporter: For their legacy. She is his legacy. She's so Pete in so many ways. Which is amazing for me. Reporter: Pete teaching us it's not how many years you have but what you make of them that counts.
This transcript has been automatically generated and may not be 100% accurate.