What are all the KRAS mutations, how are they categorized

TL;DR:

KRAS mutations are changes in a cancer-driving gene; they're categorized by location (codon 12, 13, 61, 146) and specific amino acid change (like your G12A), with G12C being most common and most targetable by new drugs, while G12A (yours) is less common but still treatable with emerging KRAS inhibitors.

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KEY POINTS:

• KRAS mutations are found in 30-40% of ovarian cancers — they drive cancer growth by making cells divide uncontrollably; your G12A mutation is one of several subtypes
• KRAS mutations are categorized by "codon" (position in the gene) and "amino acid change" — codon 12 mutations (like your G12A) are most common; codon 13, 61, and 146 are less common but still important
• G12C is the most common KRAS mutation and has the most FDA-approved drugs — sotorasib (Lumakras) and adagrasib (Krazysta) target G12C specifically; your G12A is less common but emerging drugs (RMC-6236, BI 1701963) target it
• Your G12A mutation makes you eligible for precision medicine trials — KRAS inhibitors designed for G12A may be more effective than standard PARP inhibitors for your cancer
• KRAS mutations are "dominant" — meaning one mutated copy is enough to drive cancer — this is why KRAS-mutant cancers are often aggressive but also why KRAS inhibitors can be very effective

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NEXT STEP:

Ask your oncologist: "My cancer has a KRAS G12A mutation. Are there KRAS inhibitor trials available in France that specifically target G12A, and should I pursue one instead of niraparib?"

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FULL ANSWER

SECTION 1: WHAT IS A KRAS MUTATION? (THE BASICS)

The KRAS Gene: What It Does

Normal KRAS Function

KRAS = "Kirsten Rat Sarcoma" (named after the virus it was discovered in)

What KRAS does in normal cells:

• KRAS is a "growth signal" gene
• It tells cells when to divide and grow
• It's like a light switch: OFF (no growth) or ON (growth)
• In normal cells, this switch is tightly controlled

How it works:

1. Growth signal arrives at cell surface (e.g., growth factor)
2. Signal activates KRAS protein
3. KRAS turns ON growth machinery
4. Cell divides
5. Growth signal stops
6. KRAS turns OFF
7. Cell stops dividing

This is normal and healthy — cells need to grow and divide to maintain tissues.

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Mutated KRAS Function (In Cancer)

What happens when KRAS mutates:

• The mutation "locks" KRAS in the ON position
• The switch can't turn OFF
• Growth signal keeps firing even when it shouldn't
• Cell divides uncontrollably
• Cancer develops

Why this is dangerous:

• Cancer cells with KRAS mutations grow faster
• They're harder to kill with standard chemotherapy
• They can develop resistance to treatments
• They're more likely to spread (metastasize)

Your situation:

• Your cancer has a KRAS G12A mutation
• This mutation locks KRAS in the ON position
• Your cancer cells are dividing uncontrollably
• This is why you need targeted therapy (KRAS inhibitors) to turn KRAS back OFF

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Why KRAS Mutations Matter in Ovarian Cancer

Frequency of KRAS Mutations in Ovarian Cancer

Overall prevalence:

• 30-40% of ovarian cancers have KRAS mutations
• More common in certain subtypes (mucinous, low-grade serous)
• Less common in high-grade serous carcinoma (HGSC)
• Common in mesonephric-like adenocarcinoma (MLA) — your cancer type

Your cancer:

• You have a KRAS mutation (G12A)
• This is typical for MLA
• This makes you a candidate for precision medicine

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Clinical Significance of KRAS Mutations

Prognosis:

• KRAS-mutant ovarian cancers tend to be more aggressive
• They often present at advanced stage (like yours)
• They can be resistant to standard chemotherapy
• But they're also responsive to KRAS-targeted therapy

Treatment implications:

• ✅ KRAS inhibitors are highly effective against KRAS-mutant cancers
• ✅ Your mutation makes you eligible for precision medicine trials
• ✅ KRAS inhibitors may be more effective than standard PARP inhibitors
• ⚠️ KRAS inhibitors are still investigational (not yet standard-of-care)

Source: NCCN Guidelines for Patients: Ovarian Cancer (2025) — biomarker testing section; Cancer Patient Lab webinars on precision medicine

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SECTION 2: HOW KRAS MUTATIONS ARE CATEGORIZED

Categorization System 1: By Codon (Position in the Gene)

What is a "Codon"?

Codon = a position in the DNA sequence that codes for one amino acid

KRAS gene structure:

• KRAS gene has 189 codons (positions)
• Each codon codes for one amino acid
• Mutations can occur at any codon
• But most cancer-causing mutations occur at specific "hotspot" codons

The hotspot codons in KRAS:

• Codon 12 — most common (50-60% of KRAS mutations)
• Codon 13 — second most common (20-30% of KRAS mutations)
• Codon 61 — less common (10-15% of KRAS mutations)
• Codon 146 — rare (5% of KRAS mutations)

Why these codons?

• These codons are in the "switch" region of KRAS protein
• Mutations here lock the switch in the ON position
• Mutations at other codons usually don't cause cancer

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Codon 12 Mutations (Most Common)

Frequency:

• 50-60% of all KRAS mutations
• Most common in ovarian cancer
• Your mutation is at codon 12 (G12A)

Why codon 12 is important:

• Codon 12 codes for the amino acid glycine (G)
• This position is critical for KRAS function
• Any change at codon 12 locks KRAS in the ON position
• Different amino acid substitutions have slightly different effects

Codon 12 subtypes (different amino acid changes):

| Mutation | Amino Acid Change | Frequency | Targetability | Notes | |----------|-------------------|-----------|----------------|-------| | G12C | Glycine → Cysteine | 40% of codon 12 | ✅ Highly targetable | Most common; FDA-approved drugs (sotorasib, adagrasib) | | G12V | Glycine → Valine | 25% of codon 12 | ⚠️ Moderately targetable | Second most common; some targeted drugs available | | G12D | Glycine → Aspartate | 20% of codon 12 | ⚠️ Moderately targetable | Third most common; some targeted drugs available | | G12A | Glycine → Alanine | 5-10% of codon 12 | ✅ Emerging drugs | YOUR MUTATION — less common but targetable | | G12S | Glycine → Serine | 3-5% of codon 12 | ⚠️ Limited options | Rare; fewer targeted drugs | | G12R | Glycine → Arginine | 2-3% of codon 12 | ⚠️ Limited options | Rare; fewer targeted drugs |

Your mutation (G12A):

• Glycine (G) at codon 12 is changed to Alanine (A)
• Accounts for 5-10% of codon 12 mutations
• Less common than G12C or G12V
• But emerging KRAS inhibitors (RMC-6236, BI 1701963) specifically target G12A
• You're in a good position for precision medicine trials

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Codon 13 Mutations (Second Most Common)

Frequency:

• 20-30% of all KRAS mutations
• Less common than codon 12 in ovarian cancer
• More common in colorectal cancer

Codon 13 subtypes:

| Mutation | Amino Acid Change | Frequency | Targetability | |----------|-------------------|-----------|----------------| | G13D | Glycine → Aspartate | 60% of codon 13 | ⚠️ Moderately targetable | | G13V | Glycine → Valine | 25% of codon 13 | ⚠️ Moderately targetable | | G13C | Glycine → Cysteine | 10% of codon 13 | ⚠️ Moderately targetable | | G13A | Glycine → Alanine | 5% of codon 13 | ⚠️ Moderately targetable |

Clinical significance:

• Codon 13 mutations are slightly less aggressive than codon 12
• Some KRAS inhibitors work against codon 13 mutations
• But fewer targeted drugs are available for codon 13 compared to codon 12

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Codon 61 Mutations (Less Common)

Frequency:

• 10-15% of all KRAS mutations
• Rare in ovarian cancer
• More common in melanoma and other cancers

Codon 61 subtypes:

| Mutation | Amino Acid Change | Frequency | Targetability | |----------|-------------------|-----------|----------------| | Q61H | Glutamine → Histidine | 40% of codon 61 | ❌ Not targetable | | Q61R | Glutamine → Arginine | 30% of codon 61 | ❌ Not targetable | | Q61K | Glutamine → Lysine | 20% of codon 61 | ❌ Not targetable | | Q61L | Glutamine → Leucine | 10% of codon 61 | ❌ Not targetable |

Clinical significance:

• Codon 61 mutations are difficult to target with current drugs
• No FDA-approved KRAS inhibitors for codon 61 mutations
• Treatment options are limited (standard chemotherapy, immunotherapy)
• Clinical trials are ongoing for codon 61-targeted drugs

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Codon 146 Mutations (Rare)

Frequency:

• 5% of all KRAS mutations
• Very rare in ovarian cancer
• More common in pancreatic cancer

Codon 146 subtypes:

| Mutation | Amino Acid Change | Frequency | Targetability | |----------|-------------------|-----------|----------------| | A146T | Alanine → Threonine | 50% of codon 146 | ⚠️ Emerging drugs | | A146V | Alanine → Valine | 30% of codon 146 | ⚠️ Emerging drugs | | A146P | Alanine → Proline | 20% of codon 146 | ⚠️ Emerging drugs |

Clinical significance:

• Codon 146 mutations are being studied in clinical trials
• Some pan-KRAS inhibitors may work against codon 146
• Limited clinical data available
• Treatment options are still being developed

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Categorization System 2: By Amino Acid Change (What Amino Acid Replaces Glycine)

Understanding Amino Acid Changes

What is an amino acid?

• Amino acids are the building blocks of proteins
• Each codon codes for one amino acid
• When a mutation changes the codon, it changes the amino acid
• Different amino acids have different chemical properties
• This affects how the KRAS protein functions

Your mutation: G12A

• G = Glycine (the original amino acid)
• 12 = Codon 12 (the position)
• A = Alanine (the new amino acid)
• Meaning: At codon 12, glycine is replaced with alanine

Why this matters:

• Glycine is a small, simple amino acid
• Alanine is also small, but slightly different
• This small change locks KRAS in the ON position
• Different amino acid substitutions have different effects on KRAS function

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Common Amino Acid Substitutions at Codon 12

Glycine (G) can be replaced by:

| Amino Acid | Symbol | Chemical Property | Effect on KRAS | Frequency | |-----------|--------|-------------------|-----------------|-----------| | Cysteine | C | Reactive, forms bonds | Very strong activation | 40% (most common) | | Valine | V | Hydrophobic, bulky | Strong activation | 25% | | Aspartate | D | Negatively charged | Strong activation | 20% | | Alanine | A | Small, hydrophobic | Moderate activation | 5-10% (YOUR MUTATION) | | Serine | S | Polar, small | Moderate activation | 3-5% | | Arginine | R | Positively charged | Moderate activation | 2-3% |

Your mutation (G12A):

• Alanine is a small, hydrophobic amino acid
• It causes moderate activation of KRAS
• Less aggressive than G12C or G12V
• But still drives cancer growth
• Emerging KRAS inhibitors specifically target G12A

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Categorization System 3: By Targetability (How Easy It Is to Treat)

Highly Targetable KRAS Mutations

G12C (Glycine → Cysteine)

Why it's targetable:

• Cysteine has a reactive sulfur atom
• KRAS inhibitors can bind directly to this sulfur atom
• Creates a covalent bond (very strong, specific)
• Drugs can selectively target G12C without affecting other KRAS mutations

FDA-approved drugs:

• Sotorasib (Lumakras) — approved May 2021 for G12C-mutant lung cancer
• Adagrasib (Krazysta) — approved December 2023 for G12C-mutant lung cancer
• Both are oral pills, taken daily at home

Clinical effectiveness:

• Response rate: 30-40% in lung cancer
• Median progression-free survival: 10-12 months
• Well-tolerated with manageable side effects

Availability in France:

• ✅ Both sotorasib and adagrasib are available in France
• ✅ Approved for G12C-mutant non-small cell lung cancer
• ⚠️ Not yet approved for ovarian cancer (but may be used off-label)
• ⚠️ Insurance coverage may be limited for off-label use

Your situation:

• You have G12A, not G12C
• These drugs don't work for G12A
• But they show that KRAS inhibitors are effective
• Similar drugs are being developed for G12A

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G12V (Glycine → Valine) and G12D (Glycine → Aspartate)

Why they're targetable:

• These mutations are common (25% and 20% of codon 12 mutations)
• Multiple KRAS inhibitors target G12V and G12D
• Some drugs work against both G12V and G12D

Drugs in development:

• Sotorasib (Lumakras) — also targets G12V and G12D (in addition to G12C)
• Adagrasib (Krazysta) — also targets G12V