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Tukysa (tucatinib)
Starting Tukysa can bring up a lot of questions, for you and for the people who love you. Here you'll find what to expect, how to feel your best day to day and where to get help, so you can focus on your life and time together.
ℹ️ General information to help you and your loved ones talk with your care team, not medical advice. Read our disclaimer.
Targeted therapy pill (HER2 inhibitor) · Used for: Colorectal cancer, Breast cancer
Types and tests it may fit: HER2-positive (HER2-amplified) colorectal cancer
💊 Taken by mouth · Targeted therapy pill (HER2 inhibitor)
The quick guide
What it is: Targeted therapy pill (HER2 inhibitor).
How it's given: Tablets by mouth twice a day. Combined with Herceptin (trastuzumab) for colorectal cancer, or with trastuzumab and capecitabine for breast cancer.
How it works: Tukysa blocks HER2 signaling inside cancer cells. For colorectal cancer, it's used with trastuzumab for RAS wild-type, HER2-positive cancer after standard chemo. For breast cancer it can also reach cancer in the brain.
Side effects you may notice, and what helps at home
| Side effect | What can help |
|---|---|
| Diarrhea (loose, watery stools) | Fluids, bland food; ask your team about anti-diarrhea medicine early. |
| Fatigue (extreme tiredness) | Short walks and planned rest. |
| Dermatitis (skin rash and skin changes) (Hand-foot syndrome (with capecitabine)) | Thick fragrance-free moisturizer, sunscreen, gentle soap. |
| Nausea and vomiting (CINV) | Small bland meals; take anti-nausea medicine as prescribed. |
| Mucositis (mouth sores) | Soft toothbrush and salt-and-baking-soda rinses. |
Not everyone gets these. Your team may suggest other ways to manage them.
Call your care team now if you have:
- Severe diarrhea or signs of dehydration
- Yellow skin or eyes, dark urine or belly pain (possible liver problems)
Call 911 for trouble breathing, chest pain or signs of stroke.
🗓 What to expect
1️⃣ Before you start
- Ask your team for a written schedule and an after-hours phone number.
- Bring a list of all your medicines and supplements.
2️⃣ Each day on treatment
- Take it exactly as prescribed, at about the same time each day.
- Don't crush or split pills unless your team says it's OK.
- If you miss a dose, follow the label instructions or call your pharmacist.
3️⃣ Between doses
- Watch for the side effects below and use the checklist.
- Keep up with blood tests and visits.
- Call your team for anything in the red box.
✅ Side-effect checklist
Print this and check off what you notice so you can tell your team.
| Side effect | Noticed? | Notes for my team |
|---|---|---|
| Diarrhea (loose, watery stools) | ☐ | |
| Fatigue (extreme tiredness) | ☐ | |
| Dermatitis (skin rash and skin changes) | ☐ | |
| Nausea and vomiting (CINV) | ☐ | |
| Mucositis (mouth sores) | ☐ |
Help paying for Tukysa (tucatinib)
Tukysa (tucatinib) is made by Pfizer (including former Seagen).
Official manufacturer program:
- Pfizer Oncology Together: Copay savings, benefits checks and help for people without insurance.
Copay cards are usually only for people with commercial (job or marketplace) insurance. If you have Medicare or Medicaid, look at free-drug programs and these independent foundations:
- PAN Foundation: Copays and coinsurance, including for people with Medicare, when a disease fund is open.
- HealthWell Foundation: Grants for copays, deductibles and premiums when a fund is open.
- CancerCare Co-Payment Assistance Foundation: Help with treatment copays for insured people under income limits.
- Good Days: Copay help and some travel costs.
- NeedyMeds: Free database of assistance programs, open to anyone.
📋 Medicare: Pills you take at home are usually covered by Medicare drug coverage (Part D). Part B covers some cancer drugs taken by mouth if the same drug comes in an injectable form. See Medicare and your cancer drugs.
More: Help from drug makers · Our guide to paying for cancer treatment.
❓ Questions you and your loved ones can ask
- What is the goal of this treatment for me?
- How will we know if it's working?
- Which side effects should I call about right away, and what number do I call after hours?
- Which medicines, vitamins or supplements should I avoid?
- Will this affect my ability to work, drive or care for my family?
- What will this cost me, and who can help me with coverage?
Support for you and your family
- Fight Colorectal Cancer: Patient guides, advocacy and community
- Colorectal Cancer Alliance: Helpline (877-422-2030) and patient navigation
- Susan G. Komen: Breast care helpline, treatment assistance and education
- Living Beyond Breast Cancer: Helpline, peer support and programs for metastatic breast cancer
- CancerCare: Free counseling, support groups and financial help
- Cancer Support Community: Support groups, a helpline and the MyLifeLine online community
Questions people often ask
How does Tukysa work?
Tukysa blocks HER2 signaling inside cancer cells.
How is Tukysa given?
Tablets by mouth twice a day. Combined with Herceptin (trastuzumab) for colorectal cancer, or with trastuzumab and capecitabine for breast cancer.
📄 The official FDA label for Tukysa (tucatinib), including its patient information section, is on DailyMed.
Written by the Cancer Side Effects Guide team from FDA labels and leading cancer centers. Not medical advice. · Last updated: October 15, 2026 · How we write