(CNN) - Tucked away in the quiet English countryside on more than 47 acres, GW Pharmaceuticals is doing something no other drug company can do: produce the only cannabis-based medication ever approved by the US Food and Drug Administration.
That drug, a treatment for two rare types of epilepsy, inspired researchers to consider what other conditions cannabis might help. A new clinical trial at Montefiore Medical Center in New York will examine the effect of a cannabis compound called cannabidivarin, known as CBDV, on irritability and repetitive behaviors in children with autism spectrum disorder. CBDV is a non-psychoactive chemical compound and does not cause a "high."
CNN Chief Medical Correspondent Dr. Sanjay Gupta was given exclusive access to the Montefiore study and GW Pharmaceuticals, the British biopharmaceutical company that grows the cannabis used in the trials.
Gupta got an exclusive look at one of GW's cannabis greenhouses while reporting for "Weed 5: The CBD Craze." In a grow house that spans 47 acres-- roughly 42 football fields -- GW is precisely breeding consistent strains of the cannabis plant for medicine. It's a process that has been enormously difficult to develop and master, according to the company's head of manufacturing, David Cooper. In a rare tour of GW's extraction facility, Cooper showed Gupta how GW's specialized strains of cannabis become medicine for tens of thousands of patients.
"The company's been in existence for 20 years. Epidiolex was launched towards the end of last year. So I think that journey's quite a long journey," Cooper told Gupta.
In 2018, the FDA approved Epidiolex, the first ever cannabis-based oral medication for the treatment of two rare and severe seizure disorders. Clinical trials showed it decreased seizure activity by an average of 45% to 50% in patients with Dravet syndrome, a rare and severe form of childhood-onset epilepsy. The medicine is comprised of cannabidiol, or CBD, a compound extracted from the marijuana plant.
The success of Epidiolex in treating epilepsy motivated the GW to develop a cannabis-based drug for another neurological disorder which, like severe epilepsy, has few treatment options: autism. Turns out, the two disorders share many similar behavioral symptoms.
"When you look at these -- loss of cognitive function, poor socializing skills, poor language skills -- what you're looking at is a phenotype very similar to autism," GW founder Dr. Geoffrey Guy told Gupta during a rare tour greenhouse tour. "In my mind, epilepsy and autism-type presentations are on the same continuum."
GW's CBDV is shipped from the UK to Dr. Eric Hollander, director of the Autism and Obsessive Compulsive Spectrum Program and Anxiety and Depression Program at Montefiore Hospital.
Hollander believes the cannabis extract holds hope for treating autism symptoms based on the success it's had reducing seizure activity.
"There's some abnormal electrical activity even though they don't have seizures, for example," Hollander told Gupta. "And we had previously shown that when we give anticonvulsants that decrease the electrical activity, or the spikes, some of the disruptive behaviors, or the irritability, actually get better.
"And that was one of our thoughts, why this CBDV could be helpful," Hollander said. "Because if it helps with epilepsy and it helps in terms of decreasing the spike activity, we might also get improvement in the some of the aggression, or the self-injury, or the temper tantrums."
Hollander is leading the clinical trial. With 30 years of experience in autism spectrum disorder research, Hollander also believes autism and epilepsy could have similar underlying causes.
No cure currently exists for autism. Hollander focuses on treating the associated symptoms and believes CBDV could be a breakthrough in remedying behaviors typically associated with the disorder.
"In some of the animal models that are similar to autism, it was found that CBDV had important effects on social functioning, on decreasing seizures, on increasing cognitive function, and in reducing compulsive or repetitive behavior," Hollander said. "So for that reason, we wanted to apply that to autism."
Some autism experts remain cautiously optimistic about cannabis-based medicines treating autism behaviors. Dr. Alexander Kolevzon, clinical director of the Seaver Autism Center at Mount Sinai, is not involved in the Montefiore research but is encouraged by initial reports on CBD-based cannabis medicine. Kolevzon believes cannabis compounds show enough promise to warrant further study but cautioned that the variation and range in the autism spectrum makes it an especially challenging disorder to treat.
"CBD may be helpful for only a subset of people and it may benefit different people in different ways. The challenge is to figure out which patients are likely to respond, and which symptoms are most likely to improve," Kolevzon told CNN in an email.
Similar in chemistry and benefits to CBD found in marijuana, the CBDV compound Montefiore is studying does not cause intoxication. Launched in April, the clinical trial aims to follow 100 participants ages 5-18 for 12 weeks of treatments through June 2021. It's estimated the study results will be finalized in September 2021.
For many scientists, Montefiore's study is an encouraging start, but more research must be done before conclusions are reached.
"The field of autism has a long history of enthusiasm for many treatments based on small pilot studies and anecdotal accounts," Kolevzon said. However, often when these treatments are tested rigorously in larger studies, the benefits are not significantly different than that of placebo."
Michael Morrier is the program director of Child Behavioral Interventions at the Emory Autism Center in Atlanta. He is not involved in the Montefiore study but is hopeful that patients and families will continue to focus on autism behavioral therapies in the absence of definitive data on cannabis medicines.
"Anything that's new that can be something to help a family or an individual to really be a meaningful member of their home, community, school and society is going to be helpful," Morrier said. "I would just caution that people don't just jump on the bandwagon and say, 'This is a cure all, let's do it,' because we really don't know what are the characteristics it works for, what are the behaviors it works for."
Hollander is hoping the research happening at Montefiore could provide these answers, and in doing so help patients like 14-year-old Carlos Rodriguez. While waiting for his appointment at the hospital, Carlos is playing on his iPhone and wearing a baggy sweatshirt. But it's 95 degrees, and he's wearing that sweatshirt because he can't stand how the air feels on his skin -- one of the manifestations of his autism symptoms.
Carlos was diagnosed on the autism spectrum at 4 years old. He has difficulty adapting to changes in his routine and can be triggered into angry tantrums by loud noises and crowds. After eight years of different medications to try regulating his behavior, Carlos and his mother Maribel Gonzalez are looking for better options to treat his symptoms.
Gupta was there for Carlos' intake and first dose in the study. Carlos said he wanted to join the study to better understand his own autism and help others struggling with it.
"If I don't have to worry about, like, getting angry or, like, certain schedule being broken ... I'd be pretty happy about that," he told Gupta.
The study is double-blind; neither the participants nor the doctors know if Carlos is taking the CBDV or a placebo. But Carlos and Maribel are hopeful.
"He just said, 'I hope it works, mom.' That's all he said. He said, 'I hope it works,' " Maribel told Gupta after watching her son take the first dose. "I was just like, let's see. In my head, I'm like, let's see how this goes. I mean, hopeful. Just hopeful. Really hopeful."
"I'm trying to find something that's going to help my child," she said. "Because, at the end of the day, even though he may have these disabilities, I still want my child to be somebody, do something in life. And if there's something out there that can help him reach that goal, I'll be in line."