paclitaxel
paclitaxel
Overview
Paclitaxel (brand name Taxol; Wikidata Q423762) is a diterpene natural product and microtubule-stabilizing chemotherapeutic agent originally isolated from the bark of the Pacific yew tree (Taxus brevifolia). Its primary mechanism of action involves binding to the β-tubulin subunit of assembled microtubules, hyperstabilizing the mitotic spindle and thereby arresting dividing cells in the G2/M phase of the cell cycle. Unlike vinca alkaloids, which depolymerize microtubules, paclitaxel locks tubulin polymers in a stabilized state, rendering chromosomal segregation impossible and triggering apoptosis in rapidly proliferating cancer cells. This distinctive mechanism, combined with broad-spectrum antitumor activity across breast, ovarian, lung, and several other malignancies, has established paclitaxel as one of the most widely used cytotoxic agents in oncology.
The drug's clinical utility has been complicated historically by its poor aqueous solubility, necessitating formulation with the surfactant Cremophor EL, which itself is associated with hypersensitivity reactions and altered pharmacokinetics. This limitation has driven substantial innovation in delivery science, including albumin-bound nanoparticle formulations (Nab-Paclitaxel), oral lipid-based preparations, and diverse nanoparticle platforms. Paclitaxel is routinely used in combination regimens — most prominently with carboplatin — for cancers of the breast, ovary, lung, and endometrium, and its role continues to expand through combination with modern immunotherapeutic agents such as pembrolizumab, atezolizumab, bevacizumab, and durvalumab.
Focus of Latest Publications
Recent investigations have focused on overcoming the clinical limitations of paclitaxel—principally its poor water solubility, inadequate tumor accumulation, and development of drug resistance—through advanced delivery systems and rational combination strategies. A dominant theme involves engineering nanoparticle platforms to improve pharmacokinetics and therapeutic efficacy. Studies describe chitosan-based, silk fibroin, cyclodextrin-based, metal-organic framework, and polymer-conjugate nanoparticles designed to achieve sustained and pH- or redox-responsive drug release within tumors. Many of these systems demonstrated significantly enhanced cytotoxicity compared to free paclitaxel; for example, fluorinated chitosan nanocarriers carrying paclitaxel and a photosensitizer achieved IC50 values half those of paclitaxel alone in hepatocellular carcinoma cells, while cyclodextrin-hyaluronic acid nanoparticles showed three-fold greater tumor mass reduction than traditional hydrogels in mice.
Paclitaxel combination chemotherapy has been extensively evaluated in both preclinical and clinical settings. In pancreatic cancer, co-delivery with gemcitabine via nanoparticles suppressed tumor growth and prolonged survival compared to free paclitaxel. In breast cancer, engineered nanoparticles combining paclitaxel with a Padi4 inhibitor and RAGE antagonist counteracted chemotherapy-induced metastasis by suppressing histone citrullination and epithelial-mesenchymal transition markers. Chemo-immunotherapy approaches integrated paclitaxel with immune modulators: nanoparticles co-delivering paclitaxel and the TLR7/8 agonist R848 achieved 93.2% tumor inhibition in mice by inducing immunogenic cell death and dendritic cell maturation. Clinical trials combined paclitaxel with checkpoint inhibitors; a phase II study of pembrolizumab with carboplatin/paclitaxel in melanoma reported 43% overall response rate, though without apparent survival advantage over immunotherapy alone.
At the mechanistic level, studies identified factors that modulate paclitaxel efficacy. CTDSPL2 upregulation conferred paclitaxel resistance in breast cancer through regulation of SCYL1 phosphorylation, while MARCH3 enhanced paclitaxel sensitivity in nasopharyngeal carcinoma by promoting hexokinase 2 ubiquitination and destabilization. In non-small cell lung cancer, computational analysis revealed that synergy with paclitaxel arose when partner drugs disrupted the PI3K/Akt pathway, which modulates tau protein activity. Conversely, natural product ardicrenin demonstrated anti-proliferative potency comparable to paclitaxel against osteosarcoma cells through distinct mechanisms—integrin signaling rather than microtubule stabilization.
Supportive care and alternative formulation strategies addressed paclitaxel's toxicity profile. celecoxib mitigated paclitaxel-induced peripheral neuropathy in rats by downregulating the COX-2/PGE2 pathway in dorsal root ganglia and peripheral nerves, suggesting a therapeutic target for combination studies. An oral formulation (DHP107), designed without Cremophor EL solvent, underwent food-effect evaluation in cancer patients. Biotechnological approaches included engineering Salvia miltiorrhiza hairy roots to produce taxadiene, a paclitaxel precursor, at yields of 65 mg/kg fresh weight, potentially addressing long-term supply challenges for this critical anticancer agent.