The advent of targeted cancer therapies, including monoclonalantibodies and small-moleculeinhibitors, has initiated an era of precision medical oncology focused on targeting vulnerabilities specific to cancer cells.
All modalities of anticancer therapy have the risk of causing substantial cutaneous toxicities that can seriously affect a patient’s quality of life.
What are targeted anticancer therapies?
Traditional chemotherapy utilises nonspecific properties of cytotoxic agents to impede cell division. Alternatively, the discovery of cancer-associated genemutations and hallmark-related signal transduction pathways has allowed physicians to treat cancer in a more precise manner.
What do these drugs target?
Monoclonal antibodies
Monoclonal antibodies (Mabs) target factors related to the induction of apoptosis and cell death, and prevention of angiogenesis and growth factor signalling. Recently, Mabs have been effective at leveraging the immune system to avert cancer through immune checkpoint inhibition.
Small molecule inhibitors
An assortment of small-molecule inhibitors (Nibs) have been approved to target pathways associated with the most distinctive features of cancer leading to superior overall/progression-free survival outcomes and a reduced adverse-effect profile compared with that of chemotherapy.
What are the cutaneous adverse effects of targeted therapies?
MAP Kinase Pathway
The mitogen-activated protein (MAP) kinase pathway promotes cancer survival, proliferation, angiogenesis, migration, and invasion. Frequent anticancer targets of this pathway include the protein kinases BRAF and MEK.
BRAF inhibitors
BRAF mutations are found in ~50% of melanomas. The first two BRAF inhibitors, vemurafenib and dabrafenib, are associated with significant improvement in progression-free and overall survival in patients with metastatic melanoma.
VEGF is key in moderating tumorigenesis by promoting the development of abnormal vasculature around the tumour. Current therapies targeting VEGF include bevacizumab, regorafenib, and lenvatinib.
Alterations in the fibroblast growth factor receptor (FGFR) family of tyrosine kinases have been linked to ~7% of all human cancers. Therapies targeting FGFR include erdafitinib, rogaratinib, futibatinib, infigratinib, pemigatinib, derazantinib, Debio 1347, and isogatinib.
Hallmarks of cancer associated with cell division include genomic instability, evading growth suppression, and replicative immortality. Common anticancer therapeutic targets associated with cell division and DNA repair include PARP and CDK4/6.
PARP Inhibitors
The poly(adenosine diphosphate [ADP]-ribose) polymerase (PARP) enzyme is involved in DNA repair via nucleotide and base excision repair. Therapies targeting PARP include olaparib, rucaparib, talazoparib, niraparib, and veliparib.
The G1 to S phase transition of the cell cycle is driven by cyclin-dependent kinases 4 and 6 (CDK4/6). Current anticancer therapies include abemaciclib, ribociclib, and palbociclib.
Dermatologic toxicities associated with CDK4/6 inhibitors are rare. A combination trial with aromatase inhibitor therapy reported a higher rate of rash, alopecia, pruritus, and stomatitis in the CDK4/6 and aromatase inhibitor group compared to placebo.
Chronicmyeloidleukaemia (CML) is a myeloproliferative neoplasm, resulting from the Philadelphia (Ph) chromosome balanced translocation, associated with the BCR-ABL fusion oncoprotein.Imatinib is a current therapy that targets BCR-ABL.
Primary myelofibrosis and polycythemia vera are frequently associated with mutation of the Janus kinase 2 (JAK2) non-receptor tyrosine kinase (V617F). Ruxolitinib is a current anticancer Janus kinase inhibitor.
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