A Dad Says an Experimental Autism Drug Changed His Son’s Behavior Almost Overnight, but the Promising Treatment Still Faces a Major Test

A report published October 1 by the New York Post described Matthew Bielski’s account of a dramatic change in his 4½-year-old son, Lev, after he began taking an experimental medicine called L1-79. Bielski said the improvement appeared almost immediately, with his son becoming more affectionate and engaging more frequently with his family. These observations came from the family’s experience rather than a controlled clinical assessment of Lev.

The story has attracted attention because L1-79 is being developed as a potential treatment for core autism-related symptoms involving social interaction and communication. Currently, no medications are approved specifically to treat autism’s core symptoms, although certain medications can help with associated behaviors and other conditions. The distinction between a family’s encouraging experience and the available scientific evidence is central to understanding what the reported transformation may mean.

Before Treatment, His Parents Described a Daily Struggle With Self-Injury

Before Lev began taking the experimental medicine, his parents described serious challenges involving self-injury, limited eye contact and extended periods spent away from other people. Matthew said his son sometimes hurt himself badly enough to develop significant bruising. The family’s account portrayed a household routine heavily shaped by concerns about Lev’s immediate safety.

Matthew also described dividing his time between running his business and physically preventing his son from injuring himself. According to the published report, the family was concerned that additional safety measures and antipsychotic medication might become necessary to manage the behavior. These details help explain the circumstances behind the parents’ search for another option, although the public account does not provide Lev’s complete medical records or an independent clinical evaluation.

Years of Searching for Help Led the Family to Yamo Pharmaceuticals

Matthew and his wife, Gabriella, reportedly spent years pursuing therapeutic interventions and consulting specialists before they found Yamo Pharmaceuticals, the company developing L1-79. Their search reflected the difficulties they described in managing Lev’s needs despite trying other approaches. The report does not detail every intervention they pursued or explain the individual results of those efforts.

The family’s experience helps explain why an experimental treatment showing potential could become so important to them. However, the fact that the parents had struggled to find an effective approach does not establish that every previous intervention failed or that L1-79 will work for other children. Those questions require evidence that goes beyond one family’s account, even when the reported improvements appear substantial.

What Is L1-79, the Experimental Medicine at the Center of the Story?

L1-79 is an oral investigational medicine developed by Yamo Pharmaceuticals, and the report says Lev takes it twice daily. According to Yamo’s description of the treatment, the drug inhibits tyrosine hydroxylase, an enzyme involved in producing catecholamine neurotransmitters, including dopamine and norepinephrine. The company is investigating whether altering these signaling pathways could improve aspects of social interaction and communication.

This approach differs from medications commonly prescribed to manage particular symptoms that can accompany autism, such as irritability or self-injury. Rather than focusing only on those associated behaviors, L1-79 is being studied for its potential to address core autism-related features. Its proposed mechanism remains a hypothesis under investigation, not proof that autism has one underlying biological cause or that the medicine will benefit everyone on the spectrum.

The Family Says the Improvement Began Almost Immediately

Matthew told the newspaper that he noticed a change the day after Lev began taking L1-79. He described his son becoming more affectionate and engaging with family members in ways the parents had not previously experienced to the same degree. The speed of the reported change became one of the most striking details in the family’s account.

The report also described Lev playing with his older sister, enjoying movie nights with his parents and using a letter board to spell his favorite pastime, “pool.” Matthew said his son had also begun eating solid foods, including vegetables, for the first time during the period following the treatment’s introduction. These are meaningful details about what the family observed at home, but the published account does not establish through independent testing how much each change was attributable to the medicine.

Why the Reported Changes Matter to the Family

For Lev’s parents, the reported progress involved everyday activities and interactions rather than a single dramatic moment. Greater affection, more engagement with family and new experiences around food were among the changes Matthew highlighted. Taken together, these observations help explain why he described the medicine as having transformed their family’s experience.

Personal accounts can identify possible treatment benefits that deserve further investigation, particularly when families describe changes in daily functioning. Yet an individual story cannot establish how common such a response might be, whether the improvements will continue or whether the same results would occur in other children. The report did not include a controlled assessment of Lev’s behavior before and after treatment, so the results must be understood as the family’s account.

The Larger Phase 2 Trial Studied Adolescents and Young Adults

The interest in L1-79 is not based solely on the Bielski family’s experience. In July 2024, Yamo announced results from a Phase 2 clinical trial involving 58 adolescents and young adults with autism spectrum disorder. In its announcement of the trial’s topline results, the company described a randomized, placebo-controlled crossover study.

Participants received L1-79 or a placebo during the first 12-week treatment period, followed by a six-week washout period before the treatments were switched for the next period. This design allowed researchers to compare outcomes under the two conditions. However, the participants were considerably older than Lev, who was preschool-aged during the period described in the October 2026 report, so the trial does not directly establish how the drug works in children his age.

What the Company Reported About Socialization and Safety

Yamo reported that participants receiving L1-79 showed a 7.09-point improvement over placebo on the Vineland-3 Socialization standard score during the first 12 weeks, with a reported p-value of 0.02. The company also reported statistically significant improvements on investigator-rated and caregiver-rated measures of overall symptoms. Those findings provided an early indication that the medicine might warrant additional study.

The company described L1-79 as generally well tolerated in the trial, reporting no serious adverse events or adverse events that led participants to withdraw. These findings are encouraging as preliminary results, but they do not prove that the drug is free of serious risks or that its benefits outweigh its risks for every patient. The announcement provided topline findings rather than the full detail available in a comprehensive scientific publication, making it important to distinguish the company’s report from a complete assessment of the evidence.

The Full Scientific Picture Is Still Developing

A review published in Neurotherapeutics in February 2026 examined emerging treatments being investigated for autism. The review noted that results from the placebo-controlled crossover study of L1-79 registered as NCT05067582 had not yet been published in the scientific literature at that time. This distinction matters because a company’s announcement of preliminary findings and a complete peer-reviewed study serve different purposes.

A full publication can provide detailed information about study methods, participant characteristics, outcome measures, statistical analyses and limitations. That information helps other researchers assess whether the reported effects are reliable and whether the findings justify further testing. The 2026 review of investigational autism treatments placed L1-79 among treatments still being explored, rather than presenting it as an established therapy.

The Drug’s Proposed Mechanism Remains a Hypothesis to Test

L1-79 is designed to affect catecholamine signaling, including the pathways involving dopamine and norepinephrine. These chemical messengers participate in a range of functions, and researchers are investigating whether changing their production could influence social interaction and communication for some autistic people. The treatment’s proposed mechanism offers a rationale for clinical testing, but that rationale alone cannot demonstrate effectiveness.

Autism is a spectrum, and individuals differ in their communication styles, sensory experiences, behaviors, development and support needs. A treatment that helps one person may not help another, even when they share a diagnosis. Researchers therefore need evidence from carefully designed studies to determine whether any observed benefit is reproducible, which people might benefit and what risks the treatment could carry.

Expanded Access Allowed Lev to Receive the Drug Before Approval

According to the original report, Lev received L1-79 through the FDA’s expanded-access pathway rather than waiting for the medicine to receive marketing approval. The FDA explains that expanded access can allow certain patients to obtain investigational drugs outside clinical trials under specified circumstances. Its guidance on accessing investigational medicines explains how this pathway differs from enrolling in a clinical study.

Expanded access does not mean that the FDA has approved a medicine or established that it is effective. Access depends on the circumstances, applicable requirements and involvement of the treating physician and manufacturer. For families considering an investigational treatment, those questions need to be addressed with qualified medical professionals rather than through a news report alone.

FDA Fast Track Status Does Not Mean the Drug Is Approved

L1-79 received FDA Fast Track designation in May 2018, according to Yamo’s public announcement about its clinical development. The FDA describes Fast Track as a program intended to facilitate the development and expedite the review of drugs addressing serious conditions and unmet medical needs. The designation is meant to support the development process, not to substitute for the evidence required for approval.

As of October 2026, L1-79 remains an investigational treatment rather than an FDA-approved medicine for autism. Fast Track designation does not establish that a drug has been proven safe and effective, and it does not guarantee that regulators will ultimately approve it. The distinction is important because the designation can sound more definitive than it is, especially when combined with reports of dramatic improvements in an individual child.

The Family Also Has Financial Ties to the Company Developing L1-79

The newspaper’s report disclosed that Matthew and Gabriella Bielski are investors in Yamo Pharmaceuticals. A June 2026 announcement about the Defiance Autism Impact ETF also identified Gabriella Zahn-Bielski as a member of Yamo’s board. Matthew Bielski is the chief executive of Defiance ETFs, which launched the fund to invest in companies working across autism-related areas and pledged to donate its net advisory profits to autism-focused nonprofit organizations during the fund’s first two years.

These financial connections do not establish that the family’s account of Lev’s experience is inaccurate. They are nevertheless relevant context because the family has a financial interest in a company developing the medicine they have publicly praised. Reporting both the personal experience and the financial relationships allows readers to understand the circumstances surrounding the story without assuming that either one settles the scientific questions.

Phase 3 Testing Is the Next Major Hurdle

Yamo says a pivotal Phase 3 study of L1-79 is planned for early 2027, according to its current information page for families interested in future studies. The company continues to identify the medicine as investigational and explicitly states that its safety and effectiveness have not been established. This means the treatment still needs substantial further evaluation before its potential role in autism care can be determined.

A Phase 3 study will be important for determining whether the earlier findings can be reproduced and for gathering more evidence about benefits and risks. Researchers will need to assess outcomes across a larger group of participants and examine whether any improvements are sustained. Until that evidence is available and regulators evaluate it, L1-79 cannot be considered an established treatment for autism’s core symptoms.

What Other Families Can Take From Lev’s Story

Lev’s reported experience offers a personal account of improvement that may help explain why researchers and families are watching L1-79 closely. The CDC’s overview of autism treatment explains that no medications currently treat autism’s core symptoms, although some medicines can help manage associated behaviors and co-occurring conditions. That gap in available treatments helps explain the interest in research aimed at social communication and other core features.

The central question is whether the changes described by Lev’s family can be supported by rigorous research and reproduced safely in other people. His parents’ account is a reason to follow the investigation, but it cannot predict how another child might respond or establish that the medicine caused every reported change. The significance of L1-79 will ultimately depend on the quality of the clinical evidence, the durability of any benefits and a clear understanding of its risks.