Preclinical study reports new cannabinoid that enhances tamoxifen effect in breast cancer
A journal article published online on 25 October 2026 reports a previously unidentified cannabis-derived compound, 373.15b, that lowered oestrogen receptor expression and slowed tumour growth in laboratory and mouse models. The record is a scientific abstract, not a legal or regulatory text, and it reports no human data.
Green Ark · · 2 min read
What the document is
The document is the PubMed record for a peer-reviewed journal article, "Estrogen receptor modulation by a newly-identified cannabinoid in a preclinical model of breast cancer" (PMID 42927724). It is marked "Online ahead of print", with a publication date of 25 October 2026. Only the abstract, keywords and a one-sentence summary are reproduced.
What the study reports
The authors say tumours that express oestrogen receptor alpha (ERα) and depend on oestrogen make up about 65% of breast cancer cases. Endocrine therapy for these tumours includes selective oestrogen receptor modulators (SERMs) such as tamoxifen, but many patients do not finish the recommended five, and sometimes ten, years of treatment because of adverse effects. The abstract adds that medical cannabis is increasingly used by cancer patients, mainly for palliative care, while its direct antitumour potential in breast cancer "remains poorly understood".
The work combined laboratory tests on several ER-positive breast cancer cell lines with an oestrogen-dependent xenograft mouse model. A panel of chemically distinct cannabis extracts was screened for cytotoxic activity and then tested alongside SERMs. According to the abstract, one extract, CANN14, was the only one found effective in combination with tamoxifen in the initial screen.
From that extract the authors isolated a compound they call 373.15b and describe as a novel phytocannabinoid. They report that it reproduced the extract's effect without toxicity of its own. They describe its structure as a dihydroxyphenol with an acetate group on the aromatic ring, different from known cannabinoid scaffolds.
Reported findings and limits
The abstract reports that 373.15b reduced ERα mRNA and protein levels and its transcriptional activity, "possibly" through a pathway involving RASSF1A and Hippo signalling components. In mice, it reduced tumour volume and weight, with a stronger effect when combined with tamoxifen.
The authors conclude that co-therapy with SERMs "may" allow lower doses of conventional treatment, which could reduce adverse effects. This is a statement of possibility. The abstract reports no human or clinical results, and it gives no figures on the size of the effects, the number of extracts screened or the doses used.
Who is affected
The record identifies no affected group beyond the research setting. It does not say whether 373.15b is, or could be, subject to any authorisation, scheduling or product regime, and it does not discuss development or commercialisation. Readers needing those details would have to consult the full text or other sources; the abstract does not address them.
Based on Estrogen receptor modulation by a newly-identified cannabinoid in a preclinical model of breast cancer (Authors Vered Cohen, Elazar Besser, Stav Roni Shotan, Shiri Procaccia, Adi Halle-Bikovski, Shiraz Schiller Litvinsky, Marianna Truman, Mor Harel, Sonja Thaler and David Meiri; published in Biomed Phar, 25 October 2026).
Information, not legal advice. Check the primary source before relying on it.
