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tamoxifen (tamoxifen, Douglas)

✓ Approved

Douglas Pharmaceuticals Limited · ESR1 · Small Molecule

What is tamoxifen?

tamoxifen is a small molecule developed by Douglas Pharmaceuticals Limited. It is approved for therapeutic indications via oral (po).

Drug Profile

Brand Namestamoxifen, Douglas
CompanyDouglas Pharmaceuticals Limited
Drug ClassSmall Molecule
Molecular TargetESR1
RouteOral (PO)
StatusApproved
Sources: ClinicalTrials.gov, Douglas Pharmaceuticals Limited

Mechanism of Action

Molecular Targets

tamoxifen acts on 1 molecular target:

ESR1estrogen receptor 1 (ER, ESR)
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Therapeutic Indications

tamoxifen is developed for 1 unique indication across 1 therapeutic area.

Therapeutic AreaConditionPhase
Neoplasms benign, malignant and unspecified (incl cysts and polyps)Breast cancer✓ Approved

Related Research Articles

PubMedAME case reports2026-10-14

Metastatic HER2-positive breast cancer in a 19-year-old woman following a 4-year diagnostic delay: a case report.

Ling Madeleine M, Tsavaris Nicholas N, Jenkins Amy A, Bhagat Dhruv D et al.

Breast cancer in adolescents and young adults (AYA) under age 30 is exceedingly rare, representing a very small proportion of all breast cancer cases. When it occurs, it demonstrates more aggressive biological behavior with higher rates of advanced-stage disease and poorer outcomes compared to older populations. Although breast cancer remains uncommon in this age group, population-based data demonstrate that the overall incidence of carcinomas among adolescents and AYA has increased steadily in the United States since 1975, with the greatest relative increase observed among adolescents aged 15-19 years, highlighting the importance of maintaining clinical suspicion for malignancy even in the youngest patients. A 19-year-old woman presented with a significantly enlarged left breast mass that she had first noticed at age 15 years. Initial clinical evaluation presumed a breast abscess; attempted drainage and antibiotics failed to resolve the lesion. Core needle biopsy revealed estrogen receptor (ER)-positive (70%), progesterone receptor (PR)-positive (50%), human epidermal growth factor receptor 2 (HER2)-positive infiltrating ductal carcinoma with a Ki-67 of 51%. Positron emission tomography/computed tomography (PET/CT) confirmed stage IV disease with osseous metastasis to the manubrium. She received neoadjuvant docetaxel, carboplatin, and trastuzumab with radiation therapy, achieving near-pathologic complete response. At age 21 years, she developed recurrent left breast disease and five brain metastases requiring craniotomy, CyberKnife radiosurgery, and bilateral mastectomy. Despite multiple lines of HER2-targeted therapy including ado-trastuzumab emtansine and fam-trastuzumab deruxtecan-nxki in conjunction with tamoxifen, she continues to experience ongoing disease complications at age 25 years. Germline genetic testing identified only a BRCA1 variant of uncertain significance; no pathogenic mutations were found. This case underscores the critical importance of early clinical suspicion and prompt tissue biopsy for persistent breast masses in young patients, regardless of age or presumed benign etiology. Negative genetic testing should not reduce clinical concern. Breast health education targeting AYA patients and their providers represents a modifiable opportunity to reduce diagnostic delay and improve outcomes.

PMID 42871456
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PubMedCancer investigation2026-10-13

Cancer-Associated Fibroblast Exosomes in Breast Cancer: Mechanisms of Tumor-Stroma Crosstalk and Clinical Implications.

Ghareh-Hasanlou Arezoo A, Yavari Tehrani-Fard Negar N, Akbarabadi Parastoo P, Etesami Maryam M et al.

Breast cancer progression is shaped by a continuous exchange of signals between tumor cells and the surrounding stroma, in which cancer-associated fibroblasts (CAFs) are among the most influential partners. This review concentrates on CAF-derived exosomes as the principal vehicles of that exchange, and on how their cargo and mode of delivery differ across functionally distinct CAF subtypes. Exosomes are nanoscale vesicles that carry microRNAs (miRNAs), long noncoding RNAs, proteins, and metabolites between cells, and CAF-derived vesicles have been linked to epithelial-mesenchymal transition (EMT), angiogenesis, metabolic rewiring, and resistance to chemotherapy, radiotherapy, and endocrine therapy. In estrogen receptor-positive disease, exosomal miR-22 delivered by CD63+ CAFs silences ESR1 and PTEN and blunts the response to tamoxifen, while proteins such as ADAM10 and the long noncoding RNA SNHG3 have been tied to motility and glycolytic reprogramming. The immune consequences are equally important, although the evidence here is thinner than is often implied: vesicular PD-L1 suppresses T cell priming, and spatially resolved studies now place distinct FAP+ CAF states next to specific macrophage and regulatory lymphocyte populations. Not all CAFs behave this way. Meflin+ and CD146+ subsets restrain tumor growth, which is why indiscriminate stromal depletion has repeatedly failed and why subtype-selective approaches are needed. We also consider the practical obstacles that still limit translation, including vesicle heterogeneity, the difficulty of separating exosomes from other small extracellular vesicles, and the absence of validated biomarkers.

PMID 42864691
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PubMedIntegrative cancer therapies2026-10-11

Shugan-Liangxue Prescription Inhibits Immune Escape Against Breast Cancer by Regulating Tryptophan Metabolism.

Yang Youzhan Y, Liu Jinyu J, Shi Runjia R, Li Xiaoya X et al.

ObjectiveTryptophan metabolism plays a pivotal role in promoting tumor progression by modulating immune escape in breast cancer (BC). Shugan-Liangxue prescription (SLP), a traditional Chinese medicine, has shown beneficial effects in enhancing antitumor immunity for BC treatment. This study aims to investigate the effect of SLP on tryptophan metabolism in BC and to explore the underlying mechanisms.MethodsThe immunopharmacological BC model in rats was established by chemical carcinogen induction and complete freund's adjuvant perturbations and treated with SLP. Tamoxifen and other metabolism-associated drugs were used as controls. The therapeutic efficacy of SLP was evaluated by tumor volume, weight, and oncocyte proliferation. Serum cytokines and subsets of immune cells in the spleen were measured to evaluate the anti-tumor immunity. Metabolite levels and expressions of signal molecules of tryptophan metabolic pathway were measured to explore the mechanisms.ResultsOur findings demonstrated that SLP treatment significantly inhibited tumor growth and tumor cell proliferation, and enhanced antitumor immunity by promoting Th1 polarization, increasing cytotoxic immune cells (CD8+ T cells, NKG2D+ NK cells), and reducing inhibitory immune cells (Foxp3+ Tregs, NKG2A+ NK cells, M2 macrophages) in the spleen. Additionally, SLP regulated glucose and lipid metabolism, as evidenced by reduced serum glucose and non-esterified fatty acid levels. SLP suppressed tryptophan catabolism by down-regulating expression of IDO1 and AhR and reducing kynurenine levels.ConclusionsIn summary, correlative analyses suggest SLP may mitigate breast cancer immune escape partially via the Trp metabolic pathway to boost anti-tumor immune surveillance, and its immunomodulatory activity is potentially linked to glucose and lipid reprogramming. While our findings support the involvement of the Trp-Kyn-AhR axis, causal verification via pathway rescue and inhibition assays is still needed.

PMID 42859870
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PubMedCell regeneration (London, England)2026-10-09

The generation and characterization of CTRP9-CreERT2 knock-in mice for targeting endothelial cell muscle and adipose tissues.

Wang Qingye Q, Fu Zhangxi Z, Wang Haizhen H, Ao Haiou H et al.

Vascular endothelial cells (ECs) exhibit significant diversity in different tissues. To elucidate the distinct physiological roles of individual EC subtypes, genetic mouse lines utilizing the Cre-loxP recombination system are crucial. However, there is still a lack of Cre mouse lines that specifically target muscle ECs. Here, through analysis of publicly available single-cell RNA sequencing datasets, C1q/tumor necrosis factor-related protein-9 (CTRP9) was identified as a highly selective marker for microvascular ECs in muscle and adipose tissues. A CTRP9-CreERT2-tdTomato knock-in mouse line was then generated using CRISPR/Cas9, with tdTomato serving as a reporter for endogenous CTRP9 expression. By breeding these mice with Rosa26LSL-EYFP reporter mice and administering tamoxifen, specific EYFP and tdTomato expression was observed in CD31+ ECs in the heart, skeletal muscle, tongue, and adipose tissue from postnatal to adult stages. The EYFP+ cells were mainly identified as microvascular ECs, rather than arterial or venous ECs. The CTRP9-CreERT2 mouse model allows for precise and effective genetic manipulation of this distinct endothelial population, providing a valuable tool for investigating their roles in muscle metabolism, regeneration, and pathophysiology.

PMID 42853343
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PubMedExpert opinion on drug metabolism & toxicology2026-10-09

A systematic review of oral cancer drug therapies after metabolic bariatric surgery: what oncologists need to know about altered pharmacokinetics.

Phan Aurélie A, Bastien Etienne E, Carette Claire C, Launay Manon M

Metabolic bariatric surgery (MBS) may substantially alter the pharmacokinetics of orally administered drugs, yet its impact on oral cancer drug therapies remains poorly characterized. We conducted a systematic review to synthesize the available evidence on the pharmacokinetics of oral anticancer drugs after MBS and identify practical implications for clinical management. The search was performed in PubMed, Embase and ClinicalTrials.gov. Studies reporting pharmacokinetic outcomes of oral anticancer agents after Roux-en-Y gastric bypass, sleeve gastrectomy, or one-anastomosis gastric bypass were included. Owing to heterogeneity in study design, drugs, and pharmacokinetic outcomes, a qualitative synthesis was performed. Eight studies involving 33 patients/14 oral anticancer agents were included. Exposure was generally preserved for several biopharmaceutics classification system (BCS) class-I drugs, whereas BCS class-II drugs more frequently exhibited reduced exposure, including pazopanib, sorafenib, and tamoxifen. However, substantial interindividual variability was observed across all BCS-classes, and both under- and overexposure were reported. Current evidence is scarce and of low certainty. BCS classification may assist in risk stratification, but does not reliably predict post-bariatric drug exposure. Therapeutic drug monitoring should be considered whenever available. Prospective longitudinal pharmacokinetic studies are urgently needed to establish evidence-based dosing recommendations in this growing patient population. PROSPERO registration number: CRD420261300203.

PMID 42851066
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PubMedACS applied bio materials2026-10-09

Biopolymer Silica Hybrids as Superior Nanocarriers for Anticancer Drug Delivery.

Iqbal Sumiya S, Ilyas Shaista S, Ezzat Aya A AA, Hassan Menna M et al.

Liposomal carriers are widely used for anticancer drug delivery due to their biocompatible nature in the biological milieu. Liposome-based drugs often face premature leakage, uncontrolled release, and insufficient control over long-term drug availability. Here, we present poly(lactic-co-glycolic acid) (PLGA)-coated mesoporous silica nanocarriers (PLGA-mSiO2, polysilomes) as an efficient and stable alternative to PEGylated liposomes. Such hybrid transporters are capable of efficiently encapsulating both hydrophilic [doxorubicin (DOX)] and hydrophobic [tamoxifen (TAM)] drugs. Investigation on drug loading, release kinetics, cellular uptake, and therapeutic response confirms the superior drug encapsulation and delivery of polysilomes efficiently. In liposomes, TAM was localized within the lipid bilayer, whereas DOX was actively loaded into the aqueous core through a transmembrane pH gradient. While this architecture enabled coloading, liposomes showed rapid drug release and pronounced cytotoxicity. In contrast, the core-shell structure of PLGA-mSiO2 polysilome carriers retained hydrophilic DOX within the mesoporous silica core and hydrophobic TAM within the PLGA shell. This compartmentalization ensures higher encapsulation efficiencies of both DOX (77.3%) and TAM (60.5%), with loading capacities of 59.3 and 50.4%, respectively. The PLGA-silica interface is a degradable diffusion barrier, enabling pH-responsive sustained release under acidic conditions. Moreover, PLGA-mSiO2 showed enhanced cellular uptake in MDA-MB-231 breast cancer cells and prolonged (up to 144 h) suppression of cell viability. These results present PLGA-coated mesoporous silica nanocarriers as a promising alternative to liposomal delivery by converting rapid drug release into sustained therapeutic activity.

PMID 42854092
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