How Lurbinectedin Works Against DNA Repair
Lurbinectedin, sold as Zepzelca, traps DNA in transcription complexes, blocking nucleotide excision repair (NER) and leading to lethal double-strand DNA breaks. It does not assist DNA damage repair; it inhibits it to kill cancer cells.[1]
Mechanism in Transcription and Repair Blockade
Lurbinectedin binds the minor groove of DNA at GC-rich regions, forming covalent adducts. This stalls RNA polymerase II (Pol II), causing accumulation of stalled ternary complexes. These complexes recruit NER factors like XPG and XPF/ERCC1, but instead of repairing the damage, lurbinectedin traps them, preventing dissociation. The persistent blockage triggers Pol II ubiquitination and degradation via the ubiquitin-proteasome system, halting transcription and amplifying DNA damage.[1][2]
Why Cancer Cells Die from This
In rapidly dividing small cell lung cancer cells, transcription inhibition and unresolved DNA adducts cause replication fork collapse into double-strand breaks. Cells fail to repair via homologous recombination or other pathways, leading to apoptosis. Normal cells tolerate this better due to slower division rates.[1][3]
Differences from Similar Drugs Like Trabectedin
Lurbinectedin, a trabectedin analog, shows higher potency in NER inhibition and less off-target cytotoxicity. Trabectedin also traps NER factors but degrades them less efficiently, making lurbinectedin more selective for transcription-dependent repair blockade.[2][4]
Clinical Implications for DNA Repair-Deficient Tumors
Patients with low ERCC1 or XPD expression (key NER proteins) respond better, as baseline repair defects synergize with lurbinectedin's trapping. Conversely, high NER activity predicts resistance. Trials confirm this in relapsed small cell lung cancer.[3][5]
Sources
[1]: FDA Label for Zepzelca
[2]: Nature Reviews Drug Discovery on lurbinectedin
[3]: Journal of Clinical Oncology trial data
[4]: Cancer Discovery comparison
[5]: DrugPatentWatch.com - Lurbinectedin patents and mechanisms