An Experimental Drug's Bitter End Daniel Acker for The New York Times Holly Usrey-Roos, right, with Parker, 14, and Allison, 10. Both have fragile X syndrome. Ms. Usrey-Roos said Parker was helped by the drug arbaclofen. Holly Usrey-Roos will never forget when her son, Parker, then 10, accidentally broke a drinking glass and said, "I'm sorry, Mom. I love you. Ms. Usrey-Roos with her son, Parker. The experimental drug he took for years, she said, "opened the lid and let Parker out." It was the first time she had ever heard her son say he loved her - or say much of anything for that matter. Parker, now 14, has fragile X syndrome, which causes intellectual disability and autistic behavior. Ms. Usrey-Roos is certain that Parker's new verbal ability resulted from an experimental drug he was taking in a clinical trial, and has continued to take for three years since then. She said she no longer had to wear sweaters to cover up the bruises on her arms she used to get from Parker hitting or biting her. Now, however, the drug is being taken away. It has not met the goals set for it in clinical trials testing it as a treatment for either autism or fragile X syndrome. And Seaside Therapeutics, the company developing it, is running out of money and says it can no longer afford to supply the drug to former participants in its trials. The setback is a blow in the effort to treat autism since the drug, arbaclofen, was one of the furthest along in clinical trials. And the company's decision has caused both heartbreak and outrage among some parents. "I waited 10 and a half years for him to tell me he loved me," said Ms. Usrey-Roos, who lives in Canton, Ill. With fragile X, you're like living in a box and someone is holding the lid down. The medication opened the lid and let Parker out. "I don't want to go back to the way life was," she added. The situation raises questions about what, if anything, drug companies owe to patients participating in their clinical trials. It also points out the difficulties in developing drugs to treat autism and fragile X syndrome. If the drug worked so well in some patients, why has it not succeeded so far in clinical trials? One reason is that the symptoms and behaviors associated with autism and fragile X vary widely among individuals, making it hard to capture the effects of a drug by looking at any one measure, like irritability or social withdrawal. Seaside and doctors who participated in the trials said that there were improvements in some aspects of behavior in some studies, just not those considered critical to a trial's overall success. But could it also be that the parents are deluding themselves into seeing changes that are not there? Could improvements be the result of the children simply growing older? "It's kind of hard to make the argument that the company should keep providing it if it's not working," said Dr. Michael R. Tranfaglia, medical director of the Fraxa Research Foundation, of Newburyport, Mass., which provides money for research on fragile X syndrome. Dr. Tranfaglia, whose son has fragile X but was not in a Seaside trial, said arbaclofen appeared to significantly help about a third of patients. It also made some patients worse. Without being able to tell in advance which patients would benefit, it would be hard for the drug to succeed in a clinical trial and win approval, he said. Similar situations have risen occasionally in the past. In 2004, patients with Parkinson's disease protested when Amgen stopped providing an experimental drug that some patients said had restored their lives. Amgen said the drug had failed in a clinical trial and might even be dangerous. Two patients even sued, but a court ruled the company had no obligation to continue to supply the drug to participants in its trials. In the case of arbaclofen, parents are appealing to Congress and have started an online petition hoping to find financing for the drug's development. They are also organizing through social media. Seaside executives declined to be interviewed. Until recently, Seaside, one of the few companies pursuing autism drugs, was considered a shining light by family members of those with the condition. The company, in Cambridge, Mass., grew out of the research of Mark F. Bear, a neuroscience professor at the M.I.T. Its co-founder and chief executive, Dr. Randall L. Carpenter, has a sister with an intellectual disability.