See the DrugPatentWatch profile for Koselugo
How does Koselugo (selumetinib) work?
Koselugo is a targeted cancer medicine in the MEK inhibitor class. Its mechanism of action is to block MEK1 and MEK2 kinases. By inhibiting MEK, selumetinib interrupts the MAPK/ERK signaling pathway, which many tumors rely on for growth and survival, particularly when the pathway is abnormally activated (for example, in NF1-associated disease). This pathway inhibition helps slow or stop tumor cell proliferation.
What is the pathway it targets (MAPK/ERK) and why it matters?
MEK sits in the middle of the MAPK/ERK cascade. When upstream signals activate this pathway, MEK phosphorylates downstream proteins that ultimately drive gene expression programs for cell division and survival. In tumors where the pathway is overactive, continuous MAPK/ERK signaling supports growth. Selumetinib’s MEK1/2 blockade reduces downstream signaling output, which can lead to tumor shrinkage or delayed progression.
What does MEK inhibition change inside cells?
With MEK1/2 inhibited, the downstream phosphorylation events in the ERK signaling route decrease. That reduces the signals that push cells to keep cycling and resist death, shifting tumor cells away from a “growth-promoting” signaling state.
What cancers is this mechanism used for?
Selumetinib is used for tumors where MEK/MAPK-ERK pathway activity is a key driver. In the context of NF1 (neurofibromatosis type 1), Koselugo’s MEK inhibition approach is used for certain inoperable plexiform neurofibromas because MAPK/ERK pathway signaling is implicated in their growth.
How is Koselugo’s mechanism different from other targeted treatments?
Koselugo acts downstream of upstream growth factor receptors by directly inhibiting MEK1/2. That means it targets the signaling cascade at the kinase step that converts pathway activation into downstream ERK-driven transcriptional changes, rather than blocking upstream receptors themselves.