Pyrimethamine, a dihydrofolate reductase inhibitor, has shown emerging anticancer potential but is limited by poor aqueous solubility and suboptimal bioavailability. To address these formulation challenges and improve therapeutic performance, the authors developed a nanomedicine approach using D-α-tocopheryl polyethylene glycol 1000 succinate (TPGS) to form micellar carriers for pyrimethamine.
TPGS is commonly used as a surfactant and nanocarrier component to enhance drug solubility, cellular uptake, and potential overcoming of drug resistance mechanisms. The study aimed to translate these advantages to pyrimethamine, producing a stable nanoformulation suitable for preclinical anticancer evaluation.
The primary objective was to develop and characterize a TPGS-stabilized pyrimethamine micelle formulation and to evaluate its in vitro activity in MDA-MB-231 breast cancer cells and its in vivo antitumour efficacy in a murine lymphoma model.
Micelles containing pyrimethamine were prepared using a solvent casting–rehydration technique. The formulation was assessed by dynamic light scattering (DLS), atomic force microscopy (AFM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM).
The optimized micelles were described as homogeneous and spherical, with an average diameter of about 74 nm and a low polydispersity index (PDI) of 0.20, indicating a narrow size distribution and formulation stability. Under physiological conditions the micelles demonstrated a persistent biphasic drug-release profile, consistent with sustained delivery behavior.
Compared with free pyrimethamine, the TPGS-based micellar formulation produced increased intracellular uptake and enhanced cytotoxicity in MDA-MB-231 breast cancer cells. Mechanistic assays linked these effects to oxidative stress and apoptotic signaling.
Specifically, treatment with the nanoformulation was associated with high production of reactive oxygen species (ROS), an increased proportion of Annexin V–positive cells consistent with apoptosis, and accumulation of cells in the G2/M phase of the cell cycle. The authors report that these observations collectively indicate ROS-associated apoptosis and cell-cycle arrest as contributors to the formulation’s cytotoxic activity in vitro.
The study extended evaluation to an in vivo murine lymphoma model. Treatment with the TPGS-stabilized pyrimethamine micelles reduced tumour progression in the model and resulted in 100% survival through Day 30 among treated animals. These outcomes are presented as evidence of the formulation’s antitumour potential in vivo.
The article notes the antitumour effect in the lymphoma model but does not report detailed dosing regimens, tumour-volume data, statistical analyses, or comparisons to controls in the abstract; those details were not reported in the source abstract.
Ethical approval was obtained from the Institutional Animal Ethics Committee (IAEC) with reference number BHU/DoZ/IAEC/2021-2022/014 and an IAEC meeting date reported as 15.02.2022. The approved protocol covered use of Swiss Albino BALB/c mice with 20 male and 20 female mice approved for the third year (total 40 mice). The authors declared no competing interests.
The abstract calls for additional studies to evaluate pharmacokinetic behavior and long-term safety, indicating that comprehensive safety assessment beyond the presented efficacy endpoints remains outstanding.
The TPGS-based micellar formulation of pyrimethamine produced a stable nanosystem (~74 nm, PDI 0.20) with sustained release properties. In vitro, the nanoformulation increased cellular uptake and cytotoxicity in MDA-MB-231 breast cancer cells via mechanisms consistent with elevated ROS, apoptosis (Annexin V positivity), and G2/M cell-cycle arrest. In vivo, the formulation reduced tumour progression in a murine lymphoma model and achieved 100% survival through Day 30.
The authors conclude that these findings justify further preclinical investigation of TPGS-stabilized pyrimethamine micelles as a potential anticancer delivery strategy. They explicitly note the need for additional work to confirm the detailed mechanism of action, to characterize pharmacokinetics and biodistribution, and to assess long-term safety and efficacy in breast-cancer-specific animal models.
This summary is derived solely from the PubMed/NCBI abstract (PMID: 42700206; DOI: 10.1007/s40199-026-00656-4). The abstract provides formulation parameters, key in vitro mechanistic findings, and a high-level in vivo efficacy outcome. Detailed experimental methods, full datasets, statistical analyses, dosing schedules, and expanded safety data were not included in the abstract and therefore are not reported here.