Tazemetostat: A Comprehensive Overview

Overview

Tazemetostat is utilized for treating epithelioid sarcoma, a rare, slow-growing soft tissue cancer in adults and children aged 16 and older when the cancer has spread to nearby tissues or other body parts and cannot be effectively treated with surgery. It is also prescribed for specific types of follicular lymphoma (FL), a cancer originating in white blood cells, in adults whose cancer has either relapsed or not responded to at least two previous treatments. Additionally, Tazemetostat is an option for treating follicular lymphoma in adults with no other treatment alternatives when their cancer has returned or failed to respond to prior treatments. Tazemetostat belongs to a class of medications known as EZH2 inhibitors, which prevent the spread of cancer cells. The FDA (Food and Drug Administration) approved it as an oral drug in 2020.

For Patients:

What Are the Clinical Indications for Tazemetostat?

Tazemetostat is indicated to treat advanced epithelioid sarcoma in adults aged above 18 years.

What Is the Dosage of Tazemetostat?

Tazemetostat is available in tablet form for oral administration. It is typically taken twice daily, with or without food, in 800 milligrams (mg). It is vital to take Tazemetostat at approximately the exact times each day.

What Are the Things to Inform the Doctor Before Taking the Drug?

The patient must inform the doctor if they are on other medications before starting this drug.

They should also inform them about the below-mentioned conditions:

• Pregnancy.

• Heart disease.

• Liver disease.

• Migraines.

• Seizures.

• Stroke.

• Cancer.

• Depression.

• Diabetes.

How Is Tazemetostat Administered?

Take this drug orally. One can take it with or without meals. Follow the instructions on the medication label. Take this medication as prescribed on the label simultaneously every day. Do not take the medicine more frequently than recommended. Swallow the medicine; do not chew it.

What Are the Side Effects of Tazemetostat?

• Reduced appetite.

• Feeling nauseous.

• Vomiting.

• Constipation.

• Diarrhea.

• Abdominal pain.

• Weight loss.

• Cough.

• Headache.

• Fatigue.

• Muscle, bone, or joint pain.

• Tiredness, easy bruising, fever, bone pain, or pale skin.

• Unusual bleeding.

• Skin infection.

• Shortness of breath.

Missed Dose:

If a dose is missed, it should be skipped, and the regular dosing schedule should start. A double dose should not be taken to compensate for the missed one.

Overdose:

If someone collapses, has a seizure, experiences difficulty breathing, or cannot be awakened, contact healthcare immediately.

Storage:

Store this medication in its original container, tightly sealed, and out of children's reach. Store it at room temperature, and keep it away from excessive heat and moisture (avoid storing it in the bathroom). It is crucial to keep all medications out of sight and reach of children, as many containers are not child-resistant and can be easily opened by young children.

For Doctors:

Indication:

Tazemetostat, which is a methyltransferase inhibitor, is used to treat adults aged 16 and older with metastatic or locally advanced epithelioid sarcoma when they are not eligible for complete surgical resection. This indication has been approved under accelerated approval based on the overall response rate and the duration of response.

Dose:

The recommended dosage of Tazemetostat is 800 mg, taken orally twice a day, with or without food, and continued until the disease progresses or unacceptable toxicity develops.

Dosing Considerations:

• Avoid coadministration of Tazemetostat with strong or moderate CYP3A inhibitors.

• If coadministration with a moderate CYP3A inhibitor is unavoidable, reduce the Tazemetostat dose after consulting the doctor.

• After discontinuing the moderate CYP3A inhibitor for a period equal to three elimination half-lives, resume the Tazemetostat dose that was taken before starting the inhibitor.

What Are the Pharmacological Aspects of Tazemetostat?

Mechanism of Action

Tazemetostat is a targeted cancer therapy classified as an EZH2 inhibitor. EZH2, also known as Enhancer of Zeste Homolog 2, is an essential part of the polycomb repressive complex 2 (PRC2), which plays a role in gene silencing and chromatin modification. Specifically, EZH2 catalyzes the trimethylation of histone H3 at lysine 27 (H3K27me3), a modification that leads to the repression of gene expression by altering chromatin structure and preventing transcription.

This gene silencing mechanism becomes dysregulated in many cancers, including those with certain genetic mutations or overexpression of EZH2. EZH2’s abnormal activity contributes to the silencing of tumor suppressor genes and the promotion of oncogenes, which drives tumor growth and progression.

Tazemetostat works by selectively binding to and inhibiting the enzymatic activity of EZH2. By blocking EZH2’s function, Tazemetostat reduces the levels of H3K27me3, leading to the reactivation of silenced tumor suppressor genes. This reactivation can disrupt cancer cell proliferation, induce apoptosis (programmed cell death), and inhibit tumor growth.

In particular, Tazemetostat is designed to target cancers with specific genetic mutations or overexpression of EZH2. For example, some cancers harbor mutations in the EZH2 gene itself, which result in the enzyme being constitutively active and contributing to tumorigenesis. Tazemetostat can help restore normal cellular functions and inhibit malignancy by inhibiting this aberrant activity. Tazemetostat’s selective inhibition of EZH2 provides a targeted approach to cancer treatment. It aims to minimize damage to normal cells and tissues while focusing on cancerous cells that rely on the dysregulated EZH2 pathway for their growth and survival.

Pharmacokinetics

Absorption:

• Bioavailability: Tazemetostat is administered orally as tablets. The exact oral bioavailability (the proportion of the dose that reaches systemic circulation) is not explicitly detailed in the available literature. Still, the drug is effectively absorbed into the bloodstream following oral administration.

• Peak Plasma Concentration: Tazemetostat typically achieves peak plasma concentrations within two to four hours after oral intake. This rapid absorption is important for its intended therapeutic effects.

Distribution:

• Volume of Distribution: Tazemetostat exhibits a moderate volume of distribution, suggesting that it disperses throughout body tissues beyond the bloodstream. This distribution pattern is crucial for the drug to reach its therapeutic targets effectively.

• Protein Binding: The drug is highly bound to plasma proteins, with a binding rate of approximately 99 percent. High protein binding impacts the free (active) drug concentration in the bloodstream and affects how it interacts with its target and other medications.

Metabolism:

• Primary Metabolism: Tazemetostat undergoes extensive hepatic metabolism, primarily in the liver. This metabolism involves oxidation processes facilitated by cytochrome P450 enzymes, particularly CYP3A4. This metabolic pathway is significant because it determines the drug’s clearance from the body and potential interactions with other drugs that affect CYP3A4 activity.

• Metabolites: The drug is metabolized into several metabolites, including active and inactive forms. While detailed information on the pharmacological activity of these metabolites is limited, understanding their presence helps assess the overall impact of Tazemetostat on the body.

Excretion:

• Elimination Routes: Tazemetostat is primarily eliminated through feces, with a smaller fraction excreted in the urine. This dual route of elimination helps in understanding how the drug is processed and cleared from the body.

• Half-Life: Tazemetostat's elimination half-life ranges from approximately 3 to 6 hours. This half-life affects the frequency of dosing and helps maintain therapeutic drug levels. The duration may vary based on patient-specific factors, such as liver function and concurrent medications.

Drug Interactions:

• Impact of CYP3A Inhibitors: Given that Tazemetostat is metabolized by CYP3A4, its plasma levels can be significantly affected by drugs that influence this enzyme. Strong or moderate CYP3A4 inhibitors can increase Tazemetostat levels, necessitating dose adjustments to prevent potential toxicity. Conversely, CYP3A4 inducers can lower Tazemetostat levels, reducing its therapeutic efficacy and requiring dose adjustments or alternative treatment strategies.

• Monitoring: When used in conjunction with drugs that affect CYP3A4, regular monitoring of Tazemetostat levels and patient response is essential to ensure optimal efficacy and safety.

Food Effects:

• Administration with Food: Tazemetostat can be taken with or without food. While food may alter the rate at which the drug is absorbed, it generally does not significantly impact the overall extent of absorption. This flexibility in administration helps accommodate patient preferences and minimize potential gastrointestinal discomfort.

Clinical Studies and Efficacy:

• The efficacy of Tazemetostat was studied in an open-label, single-arm cohort (Cohort 5) of a multi-center trial involving patients with confirmed metastatic or locally advanced epithelioid sarcoma.

• Patients received Tazemetostat at a dosage of 800 mg taken orally twice a day, continuing until the disease progressed or unacceptable toxicity emerged.

• Tumor responses were assessed every eight weeks, with the main measures being overall response rate (ORR) and duration of response (DOR), evaluated by blinded independent central review (BICR) using the Response Evaluation Criteria in Solid Tumors (RECIST).

• The study included 62 patients with a median age of 34 years. Most were male (63 percent) and white (76 percent). Many had prior surgery (77 percent) or systemic chemotherapy (61 percent).

• The overall response rate (ORR) was 15 percent, with two percent of patients achieving a response and 13 percent having a partial response.

• Among those who responded, 67 percent had a response lasting at least six months, with response durations ranging from four to over twenty-four months.

What Are the Contraindications of Tazemetostat?

There are no recorded contraindications to the drug till now.

Warnings and Precautions:

• Secondary Malignancies: The risk of developing secondary malignancies is elevated after treatment with Tazemetostat. In clinical trials involving 668 adults who received Tazemetostat at 800 mg twice daily, myelodysplastic syndrome (MDS) or acute myeloid leukemia (AML) was observed in 0.6 percent of patients. Additionally, one pediatric patient developed T-cell lymphoblastic lymphoma (T-LBL).

• Embryo-Fetal Toxicity: Animal studies and the drug’s mechanism of action indicate that Tazemetostat may cause harm to a fetus if given to pregnant women. There is no available data on Tazemetostat in pregnant women to determine the associated risk. Studies in pregnant rats and rabbits during organ development showed dose-dependent increases in skeletal developmental abnormalities, starting at maternal exposures about 1.5 times higher than those seen in humans at the 800 mg twice daily dose. Pregnant women should be made aware of the potential risks to the fetus. Women of childbearing age should use effective contraception while on Tazemetostat and for six months after the final dose. Men should also use effective contraception during treatment with Tazemetostat and for three months after the final dose.

Specific Considerations:

• Pregnancy: Animal studies and the drug's mechanism of action suggest that Tazemetostat can harm the fetus when given to pregnant women. There is no available data on using Tazemetostat in pregnant women to assess the associated risk. In studies with pregnant rats and rabbits, administering Tazemetostat during organ development resulted in dose-dependent skeletal abnormalities, starting at maternal exposures about 1.5 times higher than in humans at the 800 mg twice daily dose. Pregnant women should be informed about the potential risk to their fetus.

• Lactation: No information is available on the presence of Tazemetostat in human milk or its effects on breastfeeding infants. Due to the potential risk for serious adverse reactions in breastfed children, women are advised not to breastfeed during treatment with Tazemetostat and for one week after the final dose.

• Females and Males of Reproductive Potential:

  • Pregnancy Testing: Before initiating Tazemetostat treatment, it is essential to confirm the pregnancy status of females with reproductive potential.

  • Contraception: Women should use effective non-hormonal contraception during and for six months after the last dose of Tazemetostat. Some hormonal contraceptives may be less effective due to Tazemetostat. Men should use effective contraception while undergoing Tazemetostat treatment and for at least three months following the last dose.

• Pediatric Use: Tazemetostat's safety and effectiveness have been established in adolescents aged 16 with metastatic or locally advanced epithelioid sarcoma. This is supported by evidence from studies in adults and a few adolescent patients. Its safety and effectiveness in children under 16 years have yet to be established.

• Geriatric Use: There is insufficient data on patients aged 65 and older with epithelioid sarcoma to determine if they respond differently to Tazemetostat than younger patients.

• Renal Impairment: No dose adjustment of Tazemetostat is required for patients with mild to severe renal impairment or end-stage renal disease.

• Hepatic Impairment: No dose adjustment is advised for patients with mild hepatic impairment. Tazemetostat has not been studied in patients with moderate or severe hepatic impairment.