Tagrisso (Osimertinib): What It Is and What to Expect

EGFR is a receptor that sits on the surface of cells. When it is switched on, it tells the cell to grow. In some lung cancers the gene for EGFR is changed, and the switch is stuck on.

Osimertinib slips inside the cell and blocks that switch. It was designed to fit the changed version tightly, and to leave the normal EGFR on healthy skin and gut cells more alone. That is why it causes less rash and diarrhea than the older drugs in its family. The label also reports tumor responses inside the brain, which matters when lung cancer has spread there.

Tagrisso is the brand name; osimertinib is the generic name.

This drug is not for lung cancer in general. The label names the changes it treats: an exon 19 deletion, an exon 21 L858R mutation, or the T790M change that appears when an earlier EGFR drug stops working.

An FDA-approved test has to find one of these first. The test can be run on tumor tissue or, in some cases, on a blood sample. If your tumor has an EGFR change that is not on that list, this is not the matching drug, and your team will look at other options.

Osimertinib is approved at several different points in the illness. Knowing which one is yours changes what to expect.

1. After surgery has removed the tumor, to lower the chance of return.
2. For stage III cancer that cannot be removed, after chemotherapy and radiation given together.
3. As the first treatment for cancer that has spread.
4. As the first treatment for advanced disease, together with pemetrexed and platinum chemotherapy.
5. For cancer with the T790M change that has grown on an earlier EGFR drug.

The dose is one tablet daily, at roughly the same hour, with or without food. Swallow it whole if you can. People who cannot swallow tablets can ask about dispersing it in water, which the label describes.

Keep taking it on days you feel well. This drug controls the cancer only while it is in your system.

Three things get watched that patients do not always expect.

Lungs. Inflammation in the lung tissue, called interstitial lung disease, occurred in about 4 in 100 people across the trials, and a small share of those cases were fatal. Any new cough or breathlessness needs a call the same day, not at the next visit; a fever is a medical emergency and needs a call to your team at once.

Heart. Osimertinib can stretch the heart's electrical cycle, seen on an ECG as a long QT interval. It can also weaken the heart's pumping. Expect an ECG and a scan of heart function before you start and during treatment.

Eyes. Keratitis, an inflammation of the cornea, is uncommon but real. Eye pain, redness, watering, blurred vision or new trouble with bright light should be checked by an eye doctor promptly.

There is also a rare risk of aplastic anemia, where the marrow stops making blood cells. That is why blood counts are done at the start and repeated.

Loose stools, dry or cracked skin, sore or split skin around the nails, mouth ulcers and tiredness are the common ones. A simple routine helps: fragrance-free moisturizer twice a day, sunscreen, and an anti-diarrhea plan agreed in advance with your team.

Tell your team before you start any new medicine, including anything bought over the counter. Some drugs speed up the enzyme that clears osimertinib, leaving too little of it in your blood. Where that cannot be avoided, the label allows for a higher osimertinib dose — but only your prescriber can make that change. Never adjust the number of tablets yourself.

• Call 911 or go to an emergency department if you are fighting for breath at rest, your lips or fingertips turn blue, or you black out or feel your heart racing and thumping without stopping.
• Call your cancer team now, at any hour, if your temperature hits 100.4°F (38°C) or you feel feverish, shivery and unwell. CDC calls a fever during cancer treatment a medical emergency, and on this tablet a fever can also be the first sign of lung inflammation or of marrow failure. If you cannot reach them quickly, go to an emergency department. Tell whoever answers that you are taking a cancer medicine.
• Call your care team the same day if a new cough starts or your breathing gets harder than it was last week, even without a fever. Lung inflammation on this tablet is checked urgently, not at the next clinic. Ring the same day too for eye pain, a red watery eye, or vision that has gone blurry.
• Call your care team within a day or two if loose stools keep coming after you have used the anti-diarrhea plan you agreed, or the skin around a nail turns hot, swollen and painful, or mouth ulcers stop you eating.

• https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=5e81b4a7-b971-45e1-9c31-29cea8c87ce7
• https://www.cancer.gov/about-cancer/treatment/drugs/osimertinib
• https://www.cdc.gov/cancer-preventing-infections/patients/fever.html