LUNA18

What is LUNA18?

LUNA18 (international nonproprietary name paluratide) is Chugai Pharmaceutical's investigational orally-available cyclic peptide with pan-RAS inhibitory activity across diverse RAS genetic alterations — a mechanism confirmed in Sase et al. 2026 Mol Cancer Ther (PMID 42529804), the first direct LUNA18-titled primary preclinical paper. The pan-RAS framing extends beyond the initial 'pan-KRAS' concept and distinguishes LUNA18 from the G12C-specific small molecules sotorasib (Lumakras, FDA-approved 2021) and adagrasib (Krazati, FDA-approved 2022), and situates it alongside the emerging pan-RAS class that includes daraxonrasib (RMC-6236, Revolution Medicines; see Honda 2026 Cancer Sci PMID 42557936). KRAS is one of the most frequently mutated oncogenes in human cancer (~30% of all solid tumors, with particular prominence in pancreatic, colorectal, and non-small-cell lung cancer), and historically the RAS family has been considered 'undruggable' due to its smooth binding surfaces and high affinity for GTP. LUNA18 represents the macrocyclic peptide approach to RAS inhibition — using engineered cyclic peptide chemistry to bind multiple RAS mutant forms with oral bioavailability. Phase 1 dose-escalation began in 2022–2023 with cancer patients across multiple KRAS-mutant tumor types.

What LUNA18 Is Investigated For

LUNA18 (paluratide) is Chugai's lead 'middle molecule' cyclic peptide for pan-KRAS inhibition in oncology — an approach distinct from FDA-approved G12C-selective small molecules. The strongest evidence base is preclinical: structural and biochemical work demonstrating cyclic peptide binding to multiple KRAS mutant forms with oral bioavailability achieved through Chugai's middle-molecule platform. Phase 1 dose-escalation in KRAS-mutant solid tumors began in 2022–2023; published clinical efficacy data has been preliminary as of mid-2026. The honest caveats: LUNA18 is at a substantially earlier development stage than the approved KRAS inhibitors, and translating preclinical pan-KRAS activity into clinical responses in heterogeneous tumor populations has historically been difficult. The molecule is also a proof-of-concept for cyclic peptide oncology more broadly — if successful, it would validate the cyclic peptide platform for other historically undruggable protein-protein interaction targets.

History & Discovery

LUNA18 emerged from Chugai Pharmaceutical's middle-molecule drug discovery platform, which has produced multiple cyclic peptide candidates over the past decade. Chugai positioned LUNA18 as a flagship oncology candidate demonstrating that cyclic peptide chemistry can access historically 'undruggable' protein targets like KRAS while maintaining oral bioavailability. The Phase 1 dose-escalation trial in KRAS-mutant solid tumors began in 2022–2023 with results emerging through 2024–2026 at oncology conferences (ASCO, AACR) and in selected peer-reviewed publications. The molecule received its international nonproprietary name (paluratide) as part of the standard regulatory progression. LUNA18's positioning is partly clinical (extending KRAS inhibition beyond G12C) and partly platform-validating (demonstrating cyclic peptide chemistry for protein-protein interaction targets). Even if LUNA18 itself faces clinical challenges, the platform validation has implications for cyclic peptide drug discovery broadly.

How It Works

KRAS is a protein that drives many cancers by being stuck in the 'on' position. Drugs like sotorasib only work on one specific KRAS mutation (G12C). LUNA18 is designed to be a 'pan-KRAS' inhibitor — a cyclic peptide that binds to multiple KRAS mutations, potentially helping more cancer patients than the existing G12C-only drugs.

LUNA18 is a cyclic peptide engineered to bind active-state KRAS at a previously unexploited binding pocket, locking the protein in a conformation that prevents downstream signaling through RAF-MEK-ERK pathways. The 'middle molecule' approach — between small molecules (typically <500 Da) and biologics (proteins) — uses cyclic peptide chemistry to access protein-protein interaction surfaces that small molecules cannot reach, while maintaining oral bioavailability that biologics cannot achieve. The pan-RAS pharmacology targets multiple RAS mutant forms across the family (G12D, G12V, G13D, Q61L/R, and others in the diverse RAS spectrum) rather than the G12C-specific binding pocket exploited by sotorasib and adagrasib. Sase et al. 2026 Mol Cancer Ther (PMID 42529804) directly reported anti-tumor activity across diverse RAS genetic alterations in preclinical models — the definitive evidence anchor confirming the pan-RAS mechanism at the preclinical stage. Clinical translation across the RAS mutation spectrum remains an active area of trial-stage development.

Evidence Snapshot

Research Gaps & Open Questions

What the current literature has not yet settled about LUNA18:

• 01Phase 1 efficacy data publication — preliminary conference data exists but full peer-reviewed publication pending.
• 02Activity across KRAS mutation subtypes — pan-KRAS claim requires demonstration across the spectrum.
• 03Resistance mechanisms in cyclic peptide KRAS inhibition.
• 04Combination strategies with chemotherapy or other oncology agents.
• 05Long-term safety in cancer patients — not yet characterized.

Forms & Administration

Oral administration. Investigational. Not commercially available.

Dosing & Protocols

The ranges below reflect protocols commonly discussed in the literature and by clinicians — not a prescription. Actual dosing for any individual should be determined by a qualified healthcare provider who knows the patient.

LUNA18 is investigational and Phase 1 stage. Oncology management requires specialty care.

Timeline of Effects

Common Questions

Who LUNA18 Is NOT For

Drug & Supplement Interactions

Oncology drug interactions will be characterized in Phase 1/2 trials. Concurrent oncology therapy is typical for clinical trial enrollment and is managed through trial protocols.

Safety Profile

Legal Status

Regulatory status changes over time. Verify current local rules with a qualified professional.

Myths & Misconceptions