Certus250 mg

Certus 250 mg is an oral tyrosine kinase inhibitor used in the treatment of HER2-overexpressing (HER2-positive) breast cancer. HER2 status must be confirmed by an approved test before starting therapy, as efficacy depends on HER2-positive disease.

Established / FDA-approved uses

• In combination with capecitabine: for the treatment of patients with advanced or metastatic HER2-overexpressing breast cancer who have received prior therapy including an anthracycline, a taxane, and trastuzumab, and whose disease has progressed on trastuzumab.
• In combination with letrozole: for the treatment of postmenopausal women with hormone receptor-positive, HER2-overexpressing metastatic breast cancer for whom hormonal therapy is considered appropriate.

Certus 250 mg is not indicated as a single agent (monotherapy) for these indications; it must always be given in combination with capecitabine or letrozole as described above.

Each film-coated tablet contains Certus 250 mg (as Certus 250 mg ditosylate monohydrate) equivalent to 250 mg of Certus 250 mg base, along with pharmaceutically acceptable excipients including microcrystalline cellulose, povidone, sodium starch glycolate, magnesium stearate, and film-coating agents.

Certus 250 mg is a small-molecule, orally active tyrosine kinase inhibitor that dually blocks the epidermal growth factor receptor (EGFR/ErbB1) and human epidermal growth factor receptor 2 (HER2/ErbB2) signaling pathways. It is used as part of combination regimens for HER2-positive breast cancer and is supplied as 250 mg film-coated tablets for oral administration.

Certus 250 mg belongs to the class of anti-neoplastic agents, tyrosine kinase inhibitors (dual EGFR/HER2 inhibitor), used in targeted cancer therapy.

Certus 250 mg is a 4-anilinoquinazoline that reversibly inhibits the intracellular tyrosine kinase domains of both EGFR (ErbB1) and HER2 (ErbB2) receptors. By binding to the ATP-binding site of these receptors, Certus 250 mg blocks receptor autophosphorylation and downstream activation of the MAPK and PI3K/Akt signaling pathways, which are important drivers of tumor cell proliferation and survival in HER2-overexpressing breast cancer.

Pharmacokinetics: Oral bioavailability is incomplete and variable, and absorption is significantly increased (3-4 fold) by food, particularly high-fat meals. Certus 250 mg is highly protein bound (over 99%) and is extensively metabolized in the liver, primarily by CYP3A4 and to a lesser extent CYP3A5, with elimination mainly via the feces. Its terminal half-life is approximately 24 hours, supporting once-daily dosing.

Administer Certus 250 mg orally, once daily, as a single dose on an empty stomach (at least 1 hour before or after food). Do not divide the daily dose across multiple administrations, and do not crush or chew the tablets.

Certus 250 mg is primarily metabolized by CYP3A4, and clinically significant interactions include:

• Strong CYP3A4 inhibitors (e.g., ketoconazole, itraconazole, clarithromycin, ritonavir, grapefruit juice): significantly increase Certus 250 mg plasma concentrations, raising toxicity risk; concurrent use should be avoided, or the Certus 250 mg dose reduced if unavoidable.
• Strong CYP3A4 inducers (e.g., rifampin, carbamazepine, phenytoin, St. John's Wort): significantly decrease Certus 250 mg plasma concentrations, reducing efficacy; concurrent use should be avoided where possible.
• QT-prolonging drugs (e.g., certain antiarrhythmics, antipsychotics, fluoroquinolones): additive risk of QT interval prolongation when combined with Certus 250 mg; avoid concurrent use where possible and monitor ECG if unavoidable.
• P-glycoprotein and BCRP substrates (e.g., digoxin): Certus 250 mg may increase plasma concentrations of these substrates; monitor for toxicity.
• CYP2C8 substrates (e.g., certain statins such as pioglitazone, repaglinide): Certus 250 mg may increase exposure to CYP2C8 substrates.
• Acid-reducing agents (proton pump inhibitors, H2-blockers, antacids): may decrease Certus 250 mg solubility and absorption; separate dosing times where possible and discuss with a physician.

The most common adverse effects of Certus 250 mg, occurring with either combination regimen, include:

• Diarrhea (very common, can be severe — see Precautions)
• Nausea and vomiting
• Rash and other skin reactions, including palmar-plantar erythrodysesthesia (hand-foot syndrome, more common with capecitabine combination)
• Fatigue and weakness
• Decreased appetite
• Mucosal inflammation (mouth sores)
• Headache
• Back pain and extremity pain
• Dyspepsia (indigestion)
• Insomnia

Serious but less common effects (see Precautions and Warnings for full detail): hepatotoxicity (including severe, potentially fatal liver injury), QT interval prolongation, interstitial lung disease/pneumonitis, and decreased left ventricular ejection fraction (reduced heart pumping function).

Pregnancy: Certus 250 mg can cause fetal harm based on animal reproduction data showing embryo-fetal toxicity at clinically relevant exposures. Certus 250 mg should be avoided during pregnancy. Females of reproductive potential should have a pregnancy test to confirm a negative pregnancy status before starting treatment and should use effective contraception during treatment and for at least one week after the final dose. Male patients with female partners of reproductive potential should also use effective contraception during this period. If pregnancy occurs during treatment, the patient should be advised of the potential risk to the fetus and consult a physician immediately.

Lactation: It is not known whether Certus 250 mg is excreted in human milk; because of the potential for serious adverse reactions in breastfed infants, women should be advised not to breastfeed during treatment with Certus 250 mg and for at least one week after the final dose.

Hepatotoxicity

Certus 250 mg has been associated with hepatotoxicity that may be severe and, rarely, fatal. Liver function tests (ALT, AST, bilirubin) should be checked before starting treatment, every 4-6 weeks during treatment, and as clinically indicated. Certus 250 mg should be discontinued permanently in patients who develop severe changes in liver function tests, and should not be restarted.

QT Interval Prolongation

Certus 250 mg causes concentration-dependent QT interval prolongation. Correct hypokalemia and hypomagnesemia before starting treatment, and avoid use in patients with congenital long QT syndrome or who are taking other QT-prolonging medicines where possible. ECG and electrolyte monitoring should be considered, particularly in patients with cardiac risk factors.

Interstitial Lung Disease / Pneumonitis

Severe pulmonary toxicity, including interstitial lung disease and pneumonitis, has occurred with Certus 250 mg, though this is less common. Patients should be monitored for pulmonary symptoms (dyspnea, cough, fever), and Certus 250 mg should be discontinued in patients who develop severe pulmonary symptoms.

Decreased Left Ventricular Ejection Fraction (LVEF)

Certus 250 mg can reduce LVEF (heart pumping function). Cardiac function should be assessed before starting treatment (especially in patients with prior or concurrent anthracycline or trastuzumab exposure) and periodically during treatment. Treatment should be interrupted or discontinued if a significant decrease in LVEF occurs.

Diarrhea

Diarrhea is very common with Certus 250 mg and can be severe, including reports of fatal outcomes from dehydration and complications in rare cases. Proactive management with antidiarrheal medication, adequate fluid and electrolyte replacement is important; dose interruption or reduction may be necessary for severe or persistent diarrhea.

HER2 testing

Confirmation of HER2-positive status by an approved test is required before starting Certus 250 mg, as efficacy has been demonstrated only in HER2-overexpressing tumors.

Severe cutaneous reactions

Severe skin reactions, including Stevens-Johnson syndrome, have been rarely reported; discontinue permanently if a severe skin reaction occurs.

There is no specific antidote for Certus 250 mg overdose. Because Certus 250 mg is highly protein bound, dialysis is not expected to be an effective means of removing the drug. In case of suspected overdose, discontinue Certus 250 mg and seek immediate medical attention or contact emergency services/poison control; management should be supportive, with close monitoring for exaggerated adverse effects such as diarrhea, skin reactions, hepatotoxicity, and cardiac abnormalities (including QT prolongation).

Store at room temperature (below 30°C), away from light and moisture. Keep out of reach of children.

Pediatric use

The safety and effectiveness of Certus 250 mg in pediatric patients have not been established.

Geriatric use

Clinical studies of Certus 250 mg have not included sufficient numbers of patients aged 65 and over to determine whether they respond differently from younger patients; caution is advised given the greater frequency of decreased hepatic, renal, or cardiac function and comorbidities in this population.

Hepatic impairment

Dose reduction of Certus 250 mg is recommended in patients with severe hepatic impairment (see Dosage and Administration); use with caution and increased monitoring in patients with any degree of hepatic impairment.

Renal impairment

No dose adjustment is required for mild to moderate renal impairment; data in severe renal impairment are limited.

Certus 250 mg is generally continued as long as the patient is deriving clinical benefit (i.e., until disease progression or unacceptable toxicity occurs), as determined by the treating oncologist, in combination with either capecitabine or letrozole as prescribed.

Antineoplastic agent; small-molecule tyrosine kinase inhibitor; dual EGFR (ErbB1) and HER2 (ErbB2) receptor inhibitor.

Certus 250 mg reversibly binds to the intracellular ATP-binding sites of the EGFR (ErbB1) and HER2 (ErbB2) tyrosine kinase domains, blocking receptor autophosphorylation and preventing activation of downstream MAPK and PI3K/Akt signaling pathways. This dual blockade inhibits tumor cell proliferation and survival in HER2-overexpressing breast cancer cells.

The safety and effectiveness of Certus 250 mg in pediatric patients have not been established; Certus 250 mg is not approved for use in children.