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VER-01, a full-spectrum extract of cannabis, was effective and well-tolerated for treating chronic lower back pain (CLBP), according to results of a phase III study.
Publishing their findings in Nature Medicine on 29 September 2025, researchers analysed data from 820 adults with CLBP — 394 of whom took VER-01, with another 426 adults in the placebo group.
The placebo contained sesame oil, cannabis aroma and colorants to “mimic the appearance and sensory characteristics of VER-01”, the authors said.
During an initial 12-week double-blind treatment phase, the researchers observed that participants who took VER-0 saw a mean pain reduction of −1.9 numeric rating scale (NRS) points, compared with those talking placebo who reported a pain reduction of −0.6 on the same scale.
According to the results of a further open-label extension phase, those participants who took the active extract saw a further mean pain decrease to −2.9 NRS points, which continued through an additional six-month extension phase.
The participants in the VER-01 group had a mean pain intensity at baseline of 6.1 points on the NRS scale, while the mean pain intensity at baseline was 6.0 points in the placebo group.
The researchers also reported that participants in the VER-01 group “reported significant improvements in both sleep quality and physical function”, adding that “sleep quality improved by −2.2 NRS points in the VER-01 arm compared to −1.5 in the placebo arm”.
Some side effects were reported in both groups, although more were seen in the group taking VER-01.
More than four out of five participants (83.3%) in the VER-01 group reported treatment-emergent adverse events compared with 67.3% of participants in the placebo group, which included dizziness, fatigue and nausea.
However, the authors said that adverse effects were “predominantly mild to moderate, with an overall intensity comparable to placebo”.
In addition, most adverse effects occurred “during the initial titration phase, were self-limiting and declined markedly within the first few days of treatment”, the authors added.
The clinical trial was sponsored by Vertanical, who manufacture VER-01; however, the authors noted that data collation and statistical analysis were conducted by an independent clinical research organisation.
Commenting on the study, David Nutt, Edmond J Safra chair and director of the neuropsychopharmacology unit in the division of brain sciences at Imperial College London, said: “[The study] confirms what we at DrugScience and others have been saying for some time based on our T21 initiative and multi-criteria decision analysis — that whole plant extract cannabis-based products have a role in chronic pain treatment.
“Let’s hope that new research helps encourage a more rational approach to medical cannabis prescribing in the NHS where still, after nearly seven years of it being approved for use, there are less than ten scripts on the NHS. Chronic pain patients are therefore required to pay privately which, given they are often not able to work due to their condition, can be impossible.”
Mike Barnes, founder of the Medical Cannabis Clinicians Society and Cannabis Industry Council, said: “This trial is a significant step forward for the use of cannabis in chronic pain. The end points were positive and the analgesic effect lasted during the secondary phases and remained positive compared to placebo. The side effects were minimal and well tolerated.
“It adds weight to the accumulating real-world evidence that shows that cannabis is a useful and well tolerated analgesic.”
National Institute for Health and Care Excellence guidelines published in 2019 do not recommend the use of cannabis-based medicinal products for chronic pain.
In February 2025, the Scottish Intercollegiate Guidelines Network (SIGN) published draft guidance that also did not recommend the routine use of medical cannabis in the management of chronic non-malignant pain.
“Very limited evidence of clinically significant improvements in pain or wider impact… combined with consistent evidence of adverse effects/harms,” it said.
“High-quality randomised controlled trials with appropriate duration of follow up are needed to identify clinically relevant harms and benefits of medicinal cannabis in the treatment of chronic pain.”
Data from the T21 project, which collates evidence from people’s experiences of cannabis-based medical products, has revealed that pain makes up more than half (51%) of the indications for private cannabis prescriptions.
