Ocifisertib fumarate

Drug Overview

Ocifisertib fumarate (also known by its developmental code CFI-400945) is an orally bioavailable, first-in-class small-molecule inhibitor of Polo-like kinase 4 (PLK4). PLK4 is a specialized serine/threonine kinase that serves as the master regulator of centriole duplication during the cell cycle.

In the clinical landscape of March 2026, ocifisertib is recognized for its ability to induce “mitotic catastrophe” in cancer cells. By inhibiting PLK4, the drug disrupts the precise control of centrosome numbers; this leads to severe chromosomal instability, aneuploidy (abnormal chromosome counts), and eventually, programmed cell death (apoptosis). Because many cancer cells overexpress PLK4 to drive their rapid division, ocifisertib selectively targets these malignant cells while having a more limited impact on healthy, slower-dividing tissues.

• Generic Name: Ocifisertib fumarate.
• Code Name: CFI-400945; CFI-400945 fumarate.
• Drug Class: PLK4 Inhibitor; Antineoplastic Agent.
• Mechanism: Selective inhibition of Polo-like kinase 4, leading to dysregulated centriole duplication and mitotic failure.
• Route of Administration: Oral (Tablet/Capsule).
• FDA Approval Status: Investigational. As of March 2026, ocifisertib is not FDA-approved. However, it has been granted FDA Orphan Drug Designation (February 2024) and Fast Track Designation for the treatment of Acute Myeloid Leukemia (AML). It is currently in Phase 2 clinical trials for multiple indications.

What Is It and How Does It Work? (Mechanism of Action)

Ocifisertib targets the “scaffolding” required for a cancer cell to divide successfully.

1. Centriole Duplication Interference

The centriole is the core of the centrosome, the organelle that organizes the fibers that pull chromosomes apart during division.

• The PLK4 “Switch”: PLK4 acts as the “on-switch” for making a new centriole.
• Centrosome Depletion/Amplification: By blocking PLK4, ocifisertib can cause cells to have either too few or too many centrosomes. Either way, the cell cannot build a proper mitotic spindle.

2. Mitotic Catastrophe and Aneuploidy

When a cell tries to divide with a broken spindle:

• Chromosomal Chaos: The chromosomes are pulled in too many directions or not at all, leading to massive DNA damage.
• Apoptosis Induction: The cell’s internal sensors detect this “catastrophe” and trigger a suicide signal, killing the cancer cell.

3. Vulnerability in PTEN-Deficient Tumors

Preclinical research has shown that tumors lacking the PTEN protein (a common tumor suppressor) are significantly more sensitive to ocifisertib. This makes PTEN deficiency a key biomarker being used in current trials to select patients who are most likely to respond.

Clinical Indications and Status (2026)

Ocifisertib is currently being evaluated in several high-priority clinical settings:

• Acute Myeloid Leukemia (AML): This is the lead indication. It is being studied in the Phase 1b/2 TWT-202 trial for patients with relapsed or refractory AML, both as a single agent and in combination with azacitidine.
• Triple-Negative Breast Cancer (TNBC): Currently in Phase 2 trials (e.g., conducted by the Canadian Cancer Trials Group). Researchers are investigating if ocifisertib can sensitize TNBC—a notoriously difficult-to-treat subtype—to radiation therapy.
• Advanced Prostate Cancer: Being studied in Phase 2 enrichment trials for patients with metastatic castration-resistant prostate cancer, particularly those with specific genetic mutations.
• Other Solid Tumors: Investigated for potential use in lung, ovarian, and colorectal cancers where PLK4 is overexpressed.

Dosage and Administration Protocols

As an investigational agent, ocifisertib’s dosing is strictly managed within clinical trial protocols.

Safety Profile and Side Effects

The side-effect profile of ocifisertib is largely related to its effect on rapidly dividing cells, such as those in the bone marrow and gastrointestinal tract.

Common Side Effects (>20%):

• Fatigue: The most frequently reported symptom (approx. 37% of patients).
• Nausea and Vomiting: Generally mild to moderate and manageable with standard anti-emetics.
• Diarrhea: Reported in about 21% of trial participants.
• Neutropenia: A drop in white blood cell counts, which is dose-dependent and usually reversible upon stopping the drug.

Serious Risks:

• Dehydration and Anorexia: Secondary to gastrointestinal issues, requiring monitoring of fluid intake.
• Hypomagnesemia: Low magnesium levels in the blood, requiring occasional supplementation.
• Infection Risk: Due to neutropenia, patients must be monitored for fevers or other signs of illness.

Research Areas

In the fields of Stem Cell and Regenerative Medicine, ocifisertib is used to study “Centrosome Homeostasis.” Researchers are investigating how stem cells maintain their centriole counts and whether PLK4 inhibition can be used to “reprogram” the division of cancerous stem cells without harming healthy regenerative cells. In 2026, there is also intense focus on “Radiosensitization.” Scientists are using ocifisertib to block the DNA repair mechanisms that cancer cells use to survive radiation, potentially making low-dose radiation much more effective.

Patient Management and Practical Recommendations

Pre-treatment Requirements:

• Biomarker Screening: Testing for PTEN deficiency or PLK4 overexpression is often required for trial enrollment.
• Baseline Blood Work: Comprehensive CBC and metabolic panel.

“Do’s and Don’ts” List:

• DO keep a strict log of your daily doses; consistent PLK4 inhibition is required to prevent the cancer cells from “re-setting” their division cycle.
• DO report any fever higher than 38°C (100.4°F) immediately, as this could indicate neutropenic fever.
• DON’T take any new over-the-counter supplements without consulting your oncologist, as they may interfere with liver enzymes that process the drug.
• DON’T ignore persistent nausea; early intervention with anti-nausea medication can prevent dehydration.

Legal Disclaimer

The information provided is for educational and informational purposes only and does not constitute medical advice. Ocifisertib fumarate (CFI-400945) is an investigational agent and is not approved by the U.S. FDA for commercial use. Access is restricted exclusively to registered clinical trials. Always consult with a qualified oncologist or clinical investigator regarding your specific diagnosis and eligibility for research participation.