Pacritinib (Monograph)

Brand name: Vonjo
Drug class: Antineoplastic Agents

Medically reviewed by Drugs.com on Aug 29, 2023. Written by ASHP.

Introduction

Antineoplastic agent; selective inhibitor of Janus kinase (JAK) 2, mutant JAK2^V617F, and FMS-like tyrosine kinase (FLT) 3.

Uses for Pacritinib

Intermediate- or High-Risk Myelofibrosis

Treatment of adults with intermediate- or high-risk primary or secondary (post-polycythemia vera or post-essential thrombocythemia) myelofibrosis with a platelet count <50,000/mm³.

Approved under accelerated approval based on proportion of patients achieving ≥35% reduction from baseline in spleen volume; continued approval may be contingent upon verification and description of clinical benefit in confirmatory trials(s).

Designated an orphan drug by FDA for this use.

Myelofibrosis drug treatment is based upon prognostic risk models. Observation alone is advised for asymptomatic low-risk patients; for patients with higher-risk disease, allogeneic hematopoietic stem cell transplant (ASCT) is the preferred treatment. In patients who are not candidates for transplant, JAK inhibitors (i.e., ruxolitinib, pacritinib, fedratinib) may be used to provide symptom-based management and improve quality of life.

The first JAK inhibitors approved for myelofibrosis (e.g., ruxolitinib, feratinib) are associated with significant risks of hematologic toxicities. Pacritinib is an additional therapeutic option for patients with symptomatic myelofibrosis who have severe thrombocytopenia. Specific indications and toxicity profiles of the currently available JAK2 inhibitors differ; treatment should be individualized.

Pacritinib Dosage and Administration

General

Pretreatment Screening

Perform CBC including WBC differential and platelet count.
Perform coagulation testing (prothrombin time [PT], activated partial thromboplastin time [aPTT], thrombin time [TT], and international normalized ratio [INR]).
Perform baseline ECG.

Patient Monitoring

Monitor CBC including WBC differential and platelet count as clinically indicated during drug therapy.
Monitor ECG as clinically indicated during drug therapy.
Monitor for signs or symptoms of infection during drug therapy.

Other General Considerations

Discontinue or taper other kinase inhibitors according to the specific prescribing information for that drug before pacritinib initiation.
Discontinue pacritinib 7 days prior to elective surgery or invasive procedures because of the risk of hemorrhage; resume drug only after hemostasis is assured.

Administration

Oral Administration

Administer orally; take with or without food.

Swallow whole; do not open, break, or chew the capsules.

If a dose is missed, the dose should be taken at the next scheduled time. Do not take an additional dose.

Dosage

Available as pacritinib citrate; dosage expressed in terms of pacritinib.

Adults

Intermediate- or High-Risk Myelofibrosis

Oral

200 mg twice daily.

Dosage Modification for Toxicity

Oral

If adverse reactions occur during pacritinib therapy, temporary interruption of therapy, dosage reduction, and/or discontinuance of the drug may be necessary. If dosage reduction is required, the dosage of pacritinib should be reduced as described in Table 1.

Table 1: Recommended Dosage Reduction for Pacritinib Toxicity.1
Dose Reduction Level	Dosage Reduction after Recovery from Toxicity (Initial Dosage = 200 mg twice daily)
First	100 mg twice daily
Second	100 mg once daily
Third	Discontinue drug

The following table indicates the recommended dosage modification (i.e., temporary interruption of therapy, dosage reduction, discontinuance of therapy) for certain adverse effects according to severity.

Table 2. Dosage Modification for Pacritinib Toxicity.1
Adverse Reaction and Severity	Modification
Diarrhea	New onset: Initiate anti-diarrheal medications; encourage adequate oral hydration Grade 3 or 4: Withhold therapy until diarrhea improves to grade 1 or lower; resume at last given dose. Intensify antidiarrheal medications and provide fluid replacement. If diarrhea recurs, withhold therapy until resolution to grade 1 or lower or baseline; resume therapy at 50% of the last dose once toxicity has resolved. Concomitant antidiarrheal treatment is required for patients resuming drug.
Thrombocytopenia	Clinically significant worsening of thrombocytopenia that lasts >7 days: Withhold therapy until thrombocytopenia resolves; resume at 50% of the last dosage. If toxicity recurs, withhold therapy until thrombocytopenia resolves; resume at 50% of the last dosage.
Hemorrhage	Moderate bleeding; intervention indicated: Withhold therapy until bleeding resolves; resume at same dosage. If hemorrhage recurs, withhold therapy until bleeding resolves; resume at 50% of the last dosage Severe bleeding; transfusion, invasive intervention, or hospitalization indicated: Withhold therapy until bleeding resolves; resume at 50% of the last dosage. If bleeding recurs, discontinue therapy. Life-threatening bleeding; urgent intervention indicated: Discontinue therapy.
Prolonged QT Interval	QT_c prolongation >500 msec or >60 msec from baseline: Withhold therapy. If QT_c prolongation resolves to ≤480 msec or baseline within 1 week, resume at same dosage; If time to resolution is >1 week, resume therapy at a reduced dosage.

Special Populations

Hepatic Impairment

No specific dosage recommendations for patients with hepatic impairment.

Patients with Child-Pugh class B: Avoid use.

Patients with Child-Pugh class C: Avoid use.

Renal Impairment

No specific dosage recommendations for patients with renal impairment.

Patients with eGFR (MDRD) <30 mL/minute: Avoid use.

Geriatric Use

No specific dosage recommendations for geriatric patients.

Cautions for Pacritinib

Contraindications

Concomitant use of strong CYP3A4 inhibitors or inducers.

Warnings/Precautions

Hemorrhage

Serious and fatal hemorrhage reported in patients with platelet counts <100,000/mm³.

Dosage reduction, interruption, or permanent discontinuation may be required.

Avoid use in patients with active bleeding.

Hold 7 days prior to any planned surgical or invasive procedures.

Assess platelet counts periodically, as clinically indicated.

Manage hemorrhage using treatment interruption and medical intervention.

Diarrhea

Diarrhea occurs frequently; median time to resolution was 2 weeks. Incidence decreases over time; treatment interruption may be necessary.

Control pre-existing diarrhea before starting treatment. Manage with antidiarrheal medications, fluid replacement, and dosage modification.

Treat with antidiarrheal medications promptly at the first onset of symptoms. Interrupt or reduce dosage in patients with significant diarrhea despite optimal supportive care.

Thrombocytopenia

Worsening thrombocytopenia reported. Pacritinib interruption and dosage reduction may be required.

Monitor platelet count prior to treatment and as clinically indicated during treatment.

Interrupt pacritinib in patients with clinically significant worsening of thrombocytopenia that lasts for >7 days. Once the toxicity has resolved, restart at 50% of the last given dosage.

If toxicity recurs, hold pacritinib; resume the drug at 50% of the last given dose once the toxicity has resolved.

Prolonged QT Interval

Can cause prolongation of the QT_c interval. QT_c prolongation of >500 msec or increase from baseline by ≥60 msec was higher in pacritinib-treated patients than patients in the control group.

Adverse reactions related to QT_c prolongation reported; no cases of torsades de pointes reported.

Avoid use in patients with a baseline QT_c of >480 msec. Avoid concomitant use of drugs with significant potential for QT_c prolongation.

Correct hypokalemia prior to and during treatment. Manage QT_c prolongation with dose interruption and electrolyte management.

Major Adverse Cardiac Events (MACE)

Increased risk of major adverse cardiovascular events (MACE), including cardiovascular death, MI, and stroke, reported in patients receiving other JAK inhibitors for the treatment of rheumatoid arthritis.

Consider risks and benefits of pacritinib prior to initiating or continuing therapy, particularly in patients who are current or past smokers and in those with other cardiovascular risk factors. Advise patient to seek immediate medical attention if symptoms of serious cardiovascular events occur.

Thromboembolic Events

Serious and sometimes fatal thromboembolic events, including DVT, PE, and arterial thrombosis in the extremities, reported in patients receiving other JAK inhibitors for the treatment of rheumatoid arthritis.

Promptly evaluate and treat any patients who develop symptoms of thrombosis during treatment with pacritinib.

Secondary Malignancies

Another JAK inhibitor increased risk of lymphoma and other malignancies, excluding non-melanoma skin cancer (NMSC), in patients with rheumatoid arthritis.

Consider risks and benefits of pacritinib prior to initiating therapy or when considering whether to continue pacritinib, particularly in patients with a known malignancy (other than successfully treated NMSC), in those who develop a malignancy, and those who are current or past smokers.

Risk of Infection

Another JAK inhibitor increased the risk of serious infections (compared to best available therapy) in patients with myeloproliferative neoplasms.

Serious bacterial, mycobacterial, fungal, and viral infections may occur.

Resolve active serious infections prior to initiating pacritinib. Observe patients for signs and/or symptoms of infection and promptly initiate appropriate treatment.

Employ active surveillance and prophylactic antibiotics according to clinical guidelines.

Interactions with CYP3A4 Inhibitors or Inducers

Concomitant use with strong CYP3A4 inhibitors or inducers contraindicated.

Avoid concomitant use with moderate CYP3A4 inhibitors or inducers.

Specific Populations

Pregnancy

Animal studies revealed maternal toxicity and embryonic and fetal loss at dosages considerably lower than the recommended human dose.

No available human data to evaluate for a drug-associated risk of major birth defects, miscarriage, or adverse maternal or fetal outcomes related to the use of pacritinib.

Advise pregnant women of the potential risk to a fetus. Consider benefits and risks of pacritinib for the mother and possible risks to the fetus when prescribing pacritinib to a pregnant woman.

Lactation

No data on presence of pacritinib in either human or animal milk, effects on the breast-fed child, or effects on milk production.

Females should not breast-feed while receiving the drug, and for at least 2 weeks after the last dose.

Females and Males of Reproductive Potential

Reduced male mating and fertility in mice. Pacritinib may impair male fertility in humans.

Pediatric Use

Safety and efficacy not established.

Geriatric Use

Experience in patients ≥65 years of age is insufficient to determine whether geriatric patients respond differently than younger individuals.

Hepatic Impairment

Mild (Child-Pugh class A): AUC decreased by 8.5%.

Moderate (Child-Pugh class B): AUC decreased by 36%. Avoid use.

Severe hepatic impairment (Child-Pugh class C): AUC decreased by 45%. Avoid use.

Renal Impairment

eGFR 15 to 29 mL/minute: Peak plasma concentration and AUC of pacritinib increased by approximately 30%. Avoid use.

eGFR <15 mL/minute on hemodialysis: Peak plasma concentration and AUC of pacritinib increased by approximately 30%. Avoid use.

Common Adverse Effects

Adverse effects (≥20%): Diarrhea, thrombocytopenia, nausea, anemia, peripheral edema.

Drug Interactions

Metabolized mainly by CYP3A4.

Pacritinib inhibits CYP1A2, 2C19 and 3A4 and to a lesser extent CYP1A2, 2B6, 2C8, 2C9, and 2D6.

Pacritinib is an inducer of CYP1A2 and 3A4.

Pacritinib is not a substrate of breast cancer resistance protein (BCRP), multidrug resistance-associated protein (MRP) 2, organic anion-transporters (OAT) 1 and 3, organic anion-transporting polypeptides (OATP) 1B1 and 1B3, organic cation transporters (OCT) 1 and 2, or P-glycoprotein (P-gp).

Pacritinib is an inhibitor of BCRP, OCT1, OCT2, and P-gp, but not an inhibitor of bile salt export pump (BSEP), MRP2, OAT1, or OAT3.

Drugs Affecting Hepatic Microsomal Enzymes

Potent CYP3A4 inhibitors: Pharmacokinetic interaction (increased pacritinib peak plasma concentrations and AUC). Concomitant use is contraindicated.

Moderate CYP3A4 inhibitors: Pharmacokinetic interaction not studied. Avoid.

Potent CYP3A4 inducers: Pharmacokinetic interaction (decreased pacritinib peak plasma concentrations and AUC). Concomitant use is contraindicated.

Moderate CYP3A4 inducers: Pharmacokinetic interaction not studied. Avoid.

Drugs Metabolized by Hepatic Microsomal Enzymes

CYP1A2 substrates: Pharmacokinetic interaction (increased substrate plasma concentration). Avoid co-administration.

CYP 3A4 substrates: Pharmacokinetic interaction (increased substrate plasma concentration). Avoid co-administration.

Drugs Affecting or Affected by Transport Systems

P-gp substrates: Pharmacokinetic interaction (increased substrate plasma concentration). Avoid co-administration.

BCRP substrates: Pharmacokinetic interaction (increased substrate plasma concentration). Avoid co-administration.

OCT1 substrates: Pharmacokinetic interaction (increased substrate plasma concentration). Avoid co-administration.

Drugs Associated with QT Prolongation

Avoid co-administration of drugs with significant potential for QT_c prolongation with pacritinib.

Specific Drugs and Foods

Drug	Interaction	Comments
Clarithromycin	Increased peak plasma concentrations (by 30%) and AUC (by 80%)	Contraindicated. Avoid concomitant use
Rifampin	Decreased peak plasma concentrations (by 51%) and AUC (by 87%)	Contraindicated. Avoid concomitant use

Pacritinib Pharmacokinetics

Absorption

Bioavailability

Peak plasma concentrations occur in approximately 4 to 5 hours.

Steady-state is achieved within a week.

Food

No clinically relevant changes in pharmacokinetics when administered with a high-fat meal.

Special Populations

Mild (Child-Pugh class A): AUC decreased 8.5%.

Moderate (Child-Pugh class B): AUC decreased 36%.

Severe hepatic impairment (Child-Pugh class C): AUC decreased 45%.

eGFR 15 to 29 mL/minute: Peak plasma concentration and AUC of pacritinib increased by approximately 30% compared to patients with normal renal function.

eGFR <15 mL/minute on hemodialysis: Peak plasma concentration and AUC of pacritinib increased by approximately 30% compared to patients with normal renal function. .

Distribution

Plasma Protein Binding

Approximately 98.8% (mainly albumin and α₁-acidic glycoprotein).

Elimination

Metabolism

CYP3A4 is the major enzyme responsible for metabolism.

Pharmacologic activity mainly attributed to the parent molecule.

Elimination Route

Excreted in urine (6%) and feces (87%), mainly as metabolites (negligible amount as unchanged drug).

Half-life

Mean terminal half-life is 33.5 hours.

Special Populations

No clinically significant pharmacokinetic differences observed based on age, sex, body weight, or race.

Stability

Storage

Oral

Capsules

Room temperature, below 30°C.

Store in the original package; keep bottle tightly closed.

Protect from light.

Actions

Selective inhibitor of Janus kinase (JAK) 2, mutant JAK2^V617F, and FMS-like tyrosine kinase (FLT) 3.
Myelofibrosis is often associated with dysregulated JAK2 signaling.
Higher inhibitory activity for JAK2 compared to JAK3 and TYK2.
Does not inhibit JAK1 at clinically relevant concentrations.
Exhibits inhibitory activity against additional cellular kinases (such as CSF1R and IRAK1) the clinical relevance of which is unknown.

Advice to Patients

Advise patients who are currently taking a kinase inhibitor that they must taper or discontinue their current kinase inhibitor therapy according to the package insert for that drug prior to starting pacritinib.
Advise patients that pacritinib can cause hemorrhage. Inform patients about how to recognize bleeding and advise them to consult their healthcare provider right away if bleeding occurs. Patients should urgently seek emergency medical attention for any bleeding that cannot be stopped.
Advise patients that pacritinib can cause diarrhea. Advise patients to stay hydrated while taking pacritinib and to inform their physician if they experience diarrhea. Instruct patients to initiate antidiarrheal medications (e.g., loperamide) if diarrhea occurs. Advise patients to urgently seek emergency medical attention if diarrhea becomes severe.
Advise patients that pacritinib can cause thrombocytopenia, and of the need to monitor complete blood counts before and during treatment.
Advise patients to consult their healthcare provider immediately if they feel faint, lose consciousness, or have signs or symptoms suggestive of arrhythmia. Advise patients with a history of hypokalemia of the importance of monitoring their electrolytes.
Advise patients that major adverse cardiac events (MACE) including myocardial infarction, stroke, and cardiovascular death, have been reported in clinical studies with another JAK inhibitor used to treat rheumatoid arthritis, a condition for which pacritinib is not indicated. Advise patients, especially current or past smokers or patients with other cardiovascular risk factors, to be alert for the development of signs and symptoms of cardiovascular events.
Advise patients that events of deep vein thrombosis and pulmonary embolism have been reported in clinical studies with another JAK inhibitor used to treat rheumatoid arthritis, a condition for which pacritinib is not indicated. Advise patients to tell their healthcare provider if they develop any signs or symptoms of a DVT or PE.
Advise patients, especially current or past smokers and patients with a known secondary malignancy (other than a successfully treated NMSC), that lymphoma and other malignancies (excluding NMSC) have been reported in clinical studies with another JAK inhibitor used to treat rheumatoid arthritis, a condition for which pacritinib is not indicated.
Advise patients that treatment with another JAK inhibitor has increased the risk of serious infections in patients with myeloproliferative neoplasms and that serious bacterial, mycobacterial, fungal, and viral infections may occur in patients treated with pacritinib. Inform patients of the signs and symptoms of infection and to report any such signs and symptoms promptly.
Advise patients that nausea and vomiting may occur during treatment with pacritinib. Instruct them on how to manage nausea and vomiting and to immediately inform their healthcare provider if nausea/vomiting becomes severe.
Advise patients to take pacritinib twice a day, with or without food or drink. Pacritinib should be taken at similar times each day. Instruct patients to swallow the pacritinib capsules whole and not to open, break, or chew the capsules.
Instruct patients that if they miss a dose of pacritinib, to skip the dose and take the next dose when it is due and return to the normal schedule. Warn patients not to take 2 doses to make up for the missed dose.
Instruct patients to discontinue pacritinib 7 days prior to any surgery or invasive procedures (e.g., cardiac catheterization, coronary stenting or varicose vein ablation) due to the risk of bleeding and to only restart pacritinib on the instruction of their healthcare provider.
Patients should not change or stop taking pacritinib without first consulting their physician.
Importance of informing clinicians of existing or contemplated concomitant therapy, including prescription and OTC drugs, as well as any concomitant illnesses.
Importance of women informing clinicians if they are or plan to become pregnant or plan to breast-feed. Advise patients to avoid breastfeeding while taking pacritinib and for 2 weeks after the final dose.
Importance of informing patients of other important precautionary information.

Additional Information

The American Society of Health-System Pharmacists, Inc. represents that the information provided in the accompanying monograph was formulated with a reasonable standard of care, and in conformity with professional standards in the field. Readers are advised that decisions regarding use of drugs are complex medical decisions requiring the independent, informed decision of an appropriate health care professional, and that the information contained in the monograph is provided for informational purposes only. The manufacturer’s labeling should be consulted for more detailed information. The American Society of Health-System Pharmacists, Inc. does not endorse or recommend the use of any drug. The information contained in the monograph is not a substitute for medical care.

Preparations

Excipients in commercially available drug preparations may have clinically important effects in some individuals; consult specific product labeling for details.

Please refer to the ASHP Drug Shortages Resource Center for information on shortages of one or more of these preparations.

Pacritinib is available only from designated specialty distributors and pharmacies. The manufacturer should be contacted for additional information. [Web]