Paclitaxel

Paclitaxel is a chemotherapy medication in the taxane class used to treat a range of solid tumors. It acts as a microtubule stabilizer, preventing the disassembly of microtubules and thereby blocking cell division, which can lead to cancer cell death.

It was originally isolated from the bark of the Pacific yew tree (Taxus brevifolia) in the 1960s–1970s. Because of limited natural supply and environmental concerns, production shifted to semisynthetic methods and plant cell culture, with the development of solvent-based paclitaxel (Taxol) and albumin-bound paclitaxel (Abraxane).

Paclitaxel binds to beta-tubulin in microtubules, stabilizing them and preventing their normal dynamic rearrangement. This disrupts mitotic spindle formation, leading to G2/M cell-cycle arrest and the induction of apoptosis in rapidly dividing cells.

Paclitaxel is approved for metastatic ovarian cancer and is widely used in breast cancer and non-small cell lung cancer (NSCLC), among others. In ovarian cancer, it is commonly combined with carboplatin; dosing and scheduling vary by regimen and disease setting.

Paclitaxel is administered intravenously. The solvent-based formulation requires premedication to reduce hypersensitivity reactions; the albumin-bound formulation (Abraxane) avoids Cremophor EL and may have a different toxicity profile. Dosing is regimen-dependent and typically given in cycles every 1–3 weeks.

Major adverse effects include neutropenia, peripheral neuropathy, fatigue, alopecia, mucositis, and nausea. Hypersensitivity reactions can occur with the solvent-based product. Liver function and blood counts are monitored during treatment; use in pregnancy is generally avoided.

Paclitaxel is extensively hepatically metabolized by CYP2C8 and CYP3A4, with potential drug interactions for inhibitors or inducers of these enzymes and with other neurotoxic agents.