Facing advanced or metastatic breast cancer can feel overwhelming, particularly when hormone therapy stops working. In such cases, newer precision medicines can offer renewed hope. Itovebi (generic name inavolisib) is one such therapy designed to target specific genetic mutations in cancer cells. Used in combination with other treatments, Itovebi can slow tumor growth and help patients live longer, more comfortable lives.

Approved by the U.S. Food and Drug Administration in October 2024, Itovebi belongs to a class of medications known as PI3K inhibitors. It is intended for patients whose tumors harbor a PIK3CA mutation and whose cancer is hormone receptor positive (HR-positive), HER2-negative, and has become resistant to endocrine therapy.

This article helps you understand how Itovebi works, what to expect, side effects, dosing considerations, and its place in cancer treatment, all explained in patient-friendly language.

What does Itovebi do?

Itovebi is used in adults with advanced (locally advanced or metastatic) HR-positive, HER2-negative breast cancer whose cancer has progressed after hormone therapy, and whose tumor carries a PIK3CA mutation.

It is not used alone; it’s prescribed in combination with palbociclib (a CDK4/6 inhibitor) and fulvestrant (an estrogen receptor antagonist).

In clinical trials (INAVO120), adding Itovebi to the other two drugs nearly doubled progression-free survival, meaning patients on the combination lived longer without their cancer worsening (15.0 months vs. 7.3 months) compared to palbociclib + fulvestrant alone. Patients can expect that Itovebi may help delay disease progression, reduce cancer-related symptoms, and extend the period of disease control. However, individual responses vary.

How does Itovebi work?

Itovebi is a PI3K inhibitor that specifically targets the PI3Kα (alpha) isoform, which is often overactive in tumors with PIK3CA mutations.

Normally, the PI3K pathway helps cells survive, grow, and multiply. When a PIK3CA mutation is present, that pathway becomes overactive, driving cancer cells to grow unchecked. Itovebi blocks overactive signaling, thereby slowing cancer cell division and promoting cell death of mutated cells.

Importantly, Itovebi not only inhibits the mutant PI3K enzyme but also helps degrade or remove it, making it more effective at reducing the abnormal signaling in those mutated cancer cells.

Clinically, this mechanism matters because it allows the drug to attack cancer more precisely, ideally sparing normal cells and limiting side effects compared to broader chemotherapies.

Itovebi Side Effects

Like all cancer therapies, Itovebi carries a risk of side effects. Many are manageable, but some can be serious, so monitoring and prompt reporting are important.

Common side effects include:

• Hyperglycemia (high blood sugar), very common, and sometimes severe
• Mouth sores (stomatitis), common and potentially painful
• Diarrhea, including severe forms that can cause dehydration or kidney injury
• Fatigue
• Decreased blood cell counts (white blood cells, red blood cells, platelets)
• Low levels of electrolytes (calcium, potassium, magnesium)
• Elevated liver enzymes
• Rash, nausea, loss of appetite, headache
• COVID-19 infection (increased risk)

Serious side effects and warnings include:

• Severe hyperglycemia that may require insulin or dose adjustments
• Severe diarrhea causing dehydration or acute kidney injury
• Embryo-fetal toxicity (risk to unborn babies), pregnancy must be avoided
• Dose interruptions or discontinuation may be needed if side effects become severe

Patients should avoid Itovebi if they have uncontrolled high blood sugar, severe kidney disease, or if they are pregnant.

Seek medical attention if you have:

• Symptoms of very high blood sugar (e.g., thirst, frequent urination, fruity-smelling breath)
• Severe diarrheal episodes
• New or worsening mouth sores
• Signs of liver dysfunction (jaundice, dark urine)

Because Itovebi often lowers blood cell counts, doctors frequently monitor blood work to catch these problems early.

Itovebi dosage

Itovebi is taken orally (by mouth) as a tablet, usually once daily, with or without food. The FDA-approved starting dose is 9 mg once daily. If side effects occur, doses may be reduced (e.g., to 6 mg or 3 mg) or temporarily held, depending on severity.

Monitoring includes:

• Frequent blood sugar checks (fasting glucose, HbA1c) especially during the first month and periodically thereafter.
• Complete blood counts (CBC) to watch for low white cells, red cells, or platelets
• Liver function tests (ALT, AST, bilirubin)
• Electrolytes (calcium, potassium, magnesium, sodium)
• Monitoring for GI symptoms, mouth health, and hydration status

In patients with moderate renal impairment, a reduced starting dose may be considered. Treatment continues as long as the patient is benefiting, and side effects remain tolerable.

Does Itovebi Have a Generic Version?

As of 2025, no generic version of Itovebi (inavolisib) is available. It is a newly approved medication, and patent protections remain in place. However, international versions may exist in other markets.

When generic or biosimilar versions appear in the future, they will be required to show equivalent safety, purity, and effectiveness to Itovebi. Until then, patients usually receive the brand product under prescription and insurance coverage or support programs.

Conclusion

Itovebi (inavolisib) is a precision-targeted therapy newly approved for certain HR-positive, HER2-negative, PIK3CA-mutated breast cancers in patients whose disease has progressed after endocrine therapy. Used in combination with palbociclib and fulvestrant, it offers a powerful option to delay cancer progression by targeting a specific molecular driver of tumor growth.

While side effects, especially high blood sugar, diarrhea, and mouth sores can be significant, careful monitoring and dose adjustments help maximize benefit while managing risks.

If your cancer qualifies and your doctor prescribes it, Itovebi can become an important part of your treatment strategy. With a vigilant healthcare team, ongoing lab checks, and open communication, this advanced therapy may help extend disease control and improve your quality of life.

References

1. Genentech. (2024). Itovebi (inavolisib) prescribing information. itovebi+4FDA Access Data+4Gene+4
2. Drugs.com. (2024). Itovebi (inavolisib) overview, dosage, side effects. Drugs.com
3. BreastCancer.org. (2025). Inavolisib: What to expect, side effects, and more. Breastcancer.org
4. FDA. (2024). Drugs Trials Snapshot: ITOVEBI. U.S. Food and Drug Administration
5. Medscape. (2024). Itovebi (inavolisib) drug profile. Medscape Reference
6. European Medicines Agency (EMA). (2025). Itovebi EPAR overview. European Medicines Agency
7. News-Medical. (2024). Itovebi – patient medicine information. News-Medical