MET D1228 and Y1230: the wall after capmatinib and tepotinib

MET exon 14 skipping NSCLC got its first real targeted therapies in 2020. Within two years the field already had a textbook on-target resistance problem, and it lands on just two residues: D1228 and Y1230. If you work on any kinase that gets drugged with an active-state binder, this is the same trap EGFR and ALK walked into, playing out one more time.

The drugs that opened the door

MET exon 14 skipping alterations delete the juxtamembrane regulatory exon, stabilize the receptor, and drive roughly 3-4% of lung adenocarcinomas. Two type I MET tyrosine kinase inhibitors won approval on the strength of single-arm phase II data:

• Capmatinib (Tabrecta) - approved 2020 on the GEOMETRY mono-1 trial, with response rates around 68% in treatment-naive exon 14 skipping NSCLC.
• Tepotinib (Tepmetko) - approved 2021 on the VISION trial, with durable responses and the convenience of once-daily dosing.

Both are type I inhibitors: they bind the active (DFG-in) conformation of the MET kinase, wedging into the ATP pocket and hydrogen-bonding to the hinge. That binding mode is exactly what the two resistance mutations are built to disrupt.

What D1228 and Y1230 actually do

Both residues sit in the activation loop, right where a type I drug makes its closest contacts.

• Y1230 (C/H/D/S/N) - tyrosine 1230 packs directly against the inhibitor in the active-state pocket. Substituting it removes a key aromatic contact and reshapes the loop, so the type I drug loses grip. This is the single most common on-target escape mechanism reported after capmatinib or tepotinib.
• D1228 (N/V/H/Y) - aspartate 1228 is the DFG-motif aspartate that coordinates the catalytic magnesium. Mutating it shifts the conformational equilibrium and weakens the drug-kinase interaction. In the docking, you will see the activation-loop contacts that anchored the type I pose simply stop being available.

Recondo and colleagues mapped these in patients: profiling post-progression biopsies and circulating tumor DNA, they found on-target acquired resistance clustering on codons H1094, G1163, L1195, D1228, and Y1230, with D1228 and Y1230 the dominant pair. These are the residues to put on a mutation-selectivity benchmark for any MET program.

Why a type II switch sometimes rescues it

The clinically interesting twist is that D1228 and Y1230 do not behave the same way against the other inhibitor class. Type II inhibitors (cabozantinib, merestinib, glesatinib, foretinib) bind the inactive (DFG-out) conformation, reaching into the back pocket that opens when the activation loop flips out. Because they do not depend on the same active-loop contacts:

• Y1230X mutations are often still sensitive to type II inhibitors - the back-pocket binding mode tolerates the changed tyrosine.
• D1228X mutations are more stubborn. Some type II agents show reduced potency here too, because the DFG aspartate itself is part of the conformation type II drugs exploit.

That asymmetry is why sequencing a type I inhibitor into a type II inhibitor at progression is an active clinical strategy rather than a guaranteed fix. It is also a clean illustration of why conformation, not just sequence, decides whether a mutation is a resistance mutation.

Try the docking yourself

This is a conformation story, so it is worth seeing in poses rather than reading about. Open Studio, pick MET from the target catalog, and dock a type I binder against the wild-type kinase, then against the D1228 and Y1230 mutants. Watch the activation-loop contacts that hold the type I pose disappear in the mutants while the hinge interaction survives - that gap is the resistance signal. As always with mutation-selectivity work, read the ΔΔ between wild-type and mutant rather than the absolute score.

Open Studio and pick MET with D1228 or Y1230 to dock against this structure.

Liganx puts molecular docking online and free in the browser. It is a quick way to run molecular docking across MET wild-type, D1228, and Y1230 and see why the type I inhibitors hit a wall.

Primary sources

• Recondo G, Bahcall M, Spurr LF, et al. Molecular Mechanisms of Acquired Resistance to MET Tyrosine Kinase Inhibitors in Patients with MET Exon 14-Mutant NSCLC. Clin Cancer Res 26, 2615-2625 (2020). doi:10.1158/1078-0432.CCR-19-3608
• Wolf J, Seto T, Han JY, et al. Capmatinib in MET Exon 14-Mutated or MET-Amplified Non-Small-Cell Lung Cancer (GEOMETRY mono-1). N Engl J Med 383, 944-957 (2020). doi:10.1056/NEJMoa2002787
• Paik PK, Felip E, Veillon R, et al. Tepotinib in Non-Small-Cell Lung Cancer with MET Exon 14 Skipping Mutations (VISION). N Engl J Med 383, 931-943 (2020). doi:10.1056/NEJMoa2004407