Tirbanibulin for Actinic Keratosis: Dosage, Indications, Administration and Pharmacology

Overview:

Actinic keratosis (AK) is a skin condition frequently brought on by repeated exposure to ultraviolet (UV) light. It is estimated that 58 million Americans suffer from AK, with treatment expenditures exceeding $1,000,000 in 2004. Additionally, 60 percent of those over 40 with a history of UV exposure have at least one AK lesion. Scaly, rough, pink-to-red papules on sun-exposed skin are a clinical sign of AK. A histopathologic evaluation is necessary if squamous cell carcinoma (SCC) is suspected. The FDA (Food and Drug Administration) has authorized using Tirbanibulin in larger facial or scalp regions up to 100 centimeters (39.37 inches) to treat actinic keratosis. It can now be used as a topical field therapy for five days.

Drug Group:

Tirbanibulin belongs to the drug class of microtubule inhibitors.

Available Doses and Dosage Forms:

Dosage Form: Topical ointment.

Dose: The dosage of Tirbanibulin comes in 350 mg (milligrams) packages.

Topical ointment is the dose form that is applied topically to the skin.

For Patients:

What Is Actinic Keratosis?

A precancerous skin disease called actinic keratosis (AK) is brought on by prolonged exposure to ultraviolet (UV) radiation, primarily from the sun. It is a chronic illness brought on by the damaging effects of cumulative, long-term exposure to ultraviolet (UV) radiation on the epidermis. Mutations in the p53 (protein type), ras (rat sarcoma), and p16 (cyclin-dependent kinase inhibitor 2A) genes caused by UV light result in the formation of aberrant epidermal actinic keratosis (AKs) cells. These cells multiply without undergoing apoptosis (programmed cell death) and have the potential to develop into invasive squamous cell cancer.

AK manifests as rough, scaly, or crusty patches on the skin, usually on regions such as the face, lips, ears, bald scalp, neck, hands, and forearms that receive a lot of sun exposure. Topical therapies are available that are both field-directed and lesion-targeted.

If AK lesions are not treated, they may develop into squamous cell carcinoma, a kind of skin cancer.

How Does Tirbanibulin Work?

A microtubule inhibitor called Tirbanibulin prevents cells from dividing and proliferating.

Actinic keratosis lesions are thought to target and eradicate fast-proliferating precancerous and cancerous cells specifically.

Tirbanibulin causes cell cycle arrest and apoptosis (programmed cell death) in the aberrant AK cells via suppressing microtubule activity.

What Is the Dosage of Tirbanibulin?

Tirbanibulin is not for oral or ophthalmic use; only for topical application. Use one single-dose packet per application of Tirbanibulin to the treatment area on the face or scalp once a day for five days in a row.

How Effective Is Tirbanibulin?

For skin regions less than 25 cm (centimeters) (9.84 inches), or roughly the size of a baseball, Tirbanibulin treatment produced a statistically significant clearance rate of 44 percent in the first trial and 54 percent in the second trial of 353 AK patients treated in two premarketing randomized placebo-controlled studies. White males with Fitzpatrick skin (Fitzpatrick skin phototype, is a classification system used to categorize human skin color and its response to ultraviolet (UV) light exposure) types I and II who were 70 years of age or older made up the majority of participants. In patients who responded completely to Tirbanibulin, the projected recurrence rate was 47 percent. Tirbanibulin has proven to have high rates of AK lesion elimination in just five short days of therapy.

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

The following things need to be informed to the doctor before starting Tirbanibulin.

• Any additional medical disorders the patient may have, such as Tirbanibulin, may interact with specific medical problems.

• Any additional prescription drugs, vitamins, or supplements the patient is taking since there may be a potential for drug interactions.

• If the patient has any allergies, particularly to Tirbanibulin, the active ingredient, or any other component of the ointment.

• If the patient is nursing a child, intends to become pregnant, or is currently using Tirbanibulin, the effects of this medication in these circumstances are not entirely understood.

• The size and location of the actinic keratosis lesions that require medical attention.

How Is Tirbanibulin Administered?

• For five days in a row, a topical ointment called Tirbanibulin is administered once daily.

• On the face or scalp, the ointment should be applied in a thin layer to cover the afflicted region or areas, no more than 100 centimeters (9.37 inches).

• Four hours after applying the ointment, patients should cleanse the treated area or areas.

• It is not recommended to use the ointment on the interior of the nose, lips, or eyes.

What Are the Side Effects of Tirbanibulin?

• Local skin responses, pruritus at the application site, and discomfort at the application site are the most frequent adverse events (incidence ≥ two percent).

• Common cold (nasopharyngitis).

After five days of therapy, most of these adverse effects go away on their own. Any severe or enduring adverse effects should be reported by patients to their physician.

Dietary Considerations:

Patients on Tirbanibulin do not appear to have any unique dietary needs or restrictions. Unlike oral medications, Tirbanibulin is absorbed topically as a topical ointment. When taking Tirbanibulin to treat actinic keratosis, patients can keep eating normally.

Missed Dose:

• The patient should apply the missing dosage of Tirbanibulin ointment as soon as possible if they forget to take their usual dose.

• The patient should, however, forego the missed dosage and resume the normal daily administration if the next planned dose is almost here.

• It is not appropriate for patients to use more ointment to "make up" for a missed dosage.

Overdose:

• Since the active component in topical Tirbanibulin ointment is not systemically absorbed to a substantial degree, overdosing is unlikely.

• Patients should get in touch with their physician or the poison control center right away if they accidentally eat anything or apply too much topical medication.

• In the case of an overdose, supportive care can be necessary.

Storage:

• Keep in storage at room temperature between 68 degrees Fahrenheit and 77 degrees Fahrenheit (20 degrees Celsius and 25 degrees Celsius).

• Avoid freezing or refrigerating.

• Place used Tirbanibulin packages in the garbage in a safe manner.

• Keep all medications, including Tirbanibulin, out of children's reach.

For Doctors:

Indication:

Tirbanibulin is indicated for the topical treatment of actinic keratosis of the face or scalp.

Dose:

Tirbanibulin is advised to be used once daily for five days in a row.

Dosing Considerations:

• Tirbanibulin should not be consumed; it is only meant to be applied topically.
• The maximum size of the treatment area is 25 centimeters or about four inches by four inches.
• Apply and massage Tirbanibulin over the entire treated region until the drug is completely absorbed.
• Tirbanibulin application should be followed by hand washing for patients.
• Tirbanibulin is not recommended for application on open wounds, such as the lips, eyes, nose, or mouth.

What Are the Pharmacological Aspects of Tirbanibulin?

1. Pharmacodynamics

It is uncertain how Tirbanibulin treats actinic keratosis pharmacodynamically.

2. Mechanism

• The compound called Tirbanibulin binds to tubulin monomers, which are the building blocks of microtubules. By binding to tubulin monomers, Tirbanibulin inhibits the polymerization of tubulin into microtubules.

• This disruption of microtubule formation prevents proper cell division because microtubules are necessary for the separation of chromosomes during mitosis.

• Tirbanibulin's antiproliferative effect makes it a promising treatment for actinic keratosis (AKs), a precancerous skin condition.

• The inhibitory effect of Tirbanibulin on tubulin polymerization is reversible and concentration-dependent, meaning the effect can be varied by varying the dosage of the drug.

3. Pharmacokinetics

• Absorption: Tirbanibulin is absorbed through the skin following topical administration; peak plasma concentrations are usually seen two to four hours after application.

• Distribution: In the plasma, Tirbanibulin is mostly (>99 percent) protein-bound.

• Metabolism: The liver's CYP3A4 (cytochrome P450 3A4) and CYP2D6 (cytochrome P450 2D6) enzymes are principally responsible for the metabolism of Tirbanibulin.

• Elimination: A small amount is expelled in the urine, while the majority of the elimination occurs by fecal excretion.

• Half-Life: Tirbanibulin has a terminal half-life of around 24 to 36 hours.

To summarize, Tirbanibulin causes cell cycle arrest and death in rapidly dividing cells by interfering with microtubule activity. Following topical administration, it enters the body through the skin, is processed by the liver, and is mostly excreted in the feces.

Toxicity:

1. Nonclinical Toxicity

• There have not been any investigations done to determine whether Tirbanibulin can cause cancer.

• In an in vitro bacterial reverse mutation (Ames) experiment, Tirbanibulin produced a negative result. In vitro chromosomal aberration assay using Chinese hamster ovary (CHO) cells, in vitro mouse lymphoma assay using L5178/TK+/- cells, and in vivo micronucleus assay using rats all showed positive results for Tirbanibulin.

• Rats' reproductive health and fertility were evaluated with Tirbanibulin. Oral Tirbanibulin dosages of up to four mg/kg/day (milligrams per kilogram per day) in male rats and one mg/kg/day in female rats did not affect the reproductive performance of the rats. On the other hand, male rats given four mg/kg/day of Tirbanibulin orally experienced negative effects on spermatogenesis, such as decreased motility and sperm count, as well as an increase in the number of sperm with aberrant morphology.

• Males administered at two mg/kg/day had no effects on sperm.

2. Clinical Toxicity

• The most frequent adverse responses to Tirbanibulin that were documented in clinical trials included erythema (redness), pruritus (itching), and discomfort at the application site.

• The majority of these application site responses had a mild to moderate intensity and went away two weeks after the end of therapy.

• Serious adverse events that were thought to be connected to Tirbanibulin were not documented, and systemic adverse responses were rare.

Clinical Studies:

Two phase-III clinical trials assessed Tirbanibulin's safety and effectiveness in treating actinic keratosis.

When compared to vehicle (placebo) therapy, Tirbanibulin showed statistically significant improvements in the full elimination of actinic keratosis lesions in these trials.

When using Tirbanibulin, the overall clearance rates were around 44 to 47 percent, as opposed to between five and eight percent when using a vehicle. 73 percent of the 174 Tirbanibulin-treated participants who were monitored at 12 months after day 57 experienced another recurrence.

What Are the Contraindications of Tirbanibulin?

Patients who have previously experienced hypersensitivity to Tirbanibulin or any of the formulation's ingredients should not take Tirbanibulin.

Warnings and Precautions:

• Skin Reactions: The usage of Tirbanibulin has been associated with significant local skin responses, including severe dermatitis. Patients should have their local skin responses watched closely, and if they do not respond well to therapy, it should be stopped.

• Photosensitivity: Tirbanibulin may be used to treat it. During therapy, patients should be urged to wear sunscreen and restrict their time in the sun.

• Ophthalmic Toxicity: Since the safety and effectiveness of Tirbanibulin in these regions have not been verified, it is not recommended to apply it to the eyes or mucous membranes.

What Are the Drug Interactions of Tirbanibulin?

• The two enzymes that metabolize Tirbanibulin the most are CYP3A4 (Cytochrome P450 3A4) and CYP2D6 (cytochrome P450 2D6). Tirbanibulin's pharmacokinetics may be affected by the concurrent use of potent CYP3A4 inducers or inhibitors, hence this should be avoided.

• Tirbanibulin has not been the subject of formal drug interaction studies; nonetheless, there has been no assessment of possible interactions with other topically applied medications.

Specific Considerations:

• Pregnancy and Lactation: Information about the usage of Tirbanibulin in expectant or nursing mothers is not currently available. It is advisable to weigh the advantages and disadvantages of Tirbanibulin use in these groups.

• Use in Pediatrics: It is unknown if Tirbanibulin is safe or effective in treating actinic keratosis in patients under the age of 18. It is uncommon to see actinic keratosis in the pediatric population.

• Geriatric Use: In the two controlled phase 3 studies, out of the 353 participants with AK treated with Tirbanibulin, 246 (or 70 percent) were 65 years of age or older. Other reported clinical experience has not found differences in responses between the elderly and younger patients, but it cannot be ruled out that some older patients may be more sensitive than others. Overall, no differences in safety or effectiveness were observed between these subjects and younger subjects.