Rukobia (fostemsavir tromethamine)

Dosage of fostemsavir tromethamine is expressed in terms of fostemsavir.

Fostemsavir is administered orally twice daily with or without food. Swallow tablets whole; do not chew, crush, or split tablets.

If a dose of fostemsavir is missed, the prescribed dose should be taken as soon as the patient remembers. Patients should avoid missing doses due to the development of resistance. Do not double the next dose or take more than the prescribed dose.

Store fostemsavir tablets at 20-25degreesC (may be exposed to 15-30degreesC).

No dosing information is available for this tab.

Temsavir is a substrate of cytochrome P-450 (CYP) isoenzyme 3A4, P-glycoprotein (P-gp), breast cancer resistance protein (BCRP), and uridine diphosphate glucuronosyltransferase (UGT). Drugs that induce or inhibit CYP3A, P-gp, or BCRP may have an impact on temsavir concentrations.

Temsavir is an inhibitor of organic anion transporter polypeptide (OATP)1B1 and OATP1B3. Additionally, temsavir and 2 of tis metabolites are inhibitors of BCRP.

At clinically relevant concentrations, significant interactions are not expected based on in vitro and clinical drug interaction results when fostemsavir is administered with substrates of CYP1A2, 2A6, 2B6, 2C8, 2C9, 2C19, 2E1, 2D6, and 3A4; UGT1A1, 1A4, 1A6, 1A9, 2B7; P-gp, multidrug resistance protein (MRP)2; bile salt export pump (BSEP); sodium taurocholate co-transporting polypeptide (NTCP); multidrug and toxin extrusion protein (MATE)1/2K; organic anion transporters (OAT)1 and OAT3; and organic cation transporters (OCT)1 and OCT2.

Contraindicated Drug Combination: This drug combination is contraindicated and generally should not be dispensed or administered to the same patient.

Anti-Retrovirals/Atidarsagene Autotemcel

SEVERITY LEVEL: 1-Contraindicated Drug Combination: This drug combination is contraindicated and generally should not be dispensed or administered to the same patient.

MECHANISM OF ACTION: Atidarsagene autotemcel is prepared from apheresed cells that are transduced with a replication defective, self-inactivating lentiviral vector. Antiretrovirals may interfere with the manufacturing of apheresed cells.

CLINICAL EFFECTS: Use of antiretrovirals before mobilization and apheresis may interfere with the production of atidarsagene autotemcel.

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: Discontinue antiretrovirals for at least one month prior to mobilization (or the expected duration of time needed for elimination of the medication) until all cycles of apheresis are completed. If a patient requires antiretrovirals for HIV prophylaxis, then confirm a negative HIV test before beginning mobilization and apheresis of CD34+ cells.

DISCUSSION: Antiretroviral medications may interfere with the manufacturing of atidarsagene autotemcel therapy.(1)

Anti-Retrovirals/Elivaldogene Autotemcel

SEVERITY LEVEL: 1-Contraindicated Drug Combination: This drug combination is contraindicated and generally should not be dispensed or administered to the same patient.

MECHANISM OF ACTION: Elivaldogene autotemcel is prepared from apheresed cells that are transduced with a replication defective, self-inactivating lentiviral vector. Antiretrovirals may interfere with the manufacturing of apheresed cells.

CLINICAL EFFECTS: Use of antiretrovirals before mobilization and apheresis may interfere with the production of elivaldogene autotemcel.

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: Discontinue antiretrovirals for at least one month prior to mobilization and until all cycles of apheresis are completed. If a patient requires antiretrovirals for HIV prophylaxis, then confirm a negative HIV test before beginning mobilization and apheresis of CD34+ cells.

DISCUSSION: Antiretroviral medications may interfere with the manufacturing of elivaldogene autotemcel therapy.(1)

Anti-Retrovirals/Etuvetidigene Autotemcel

SEVERITY LEVEL: 1-Contraindicated Drug Combination: This drug combination is contraindicated and generally should not be dispensed or administered to the same patient.

MECHANISM OF ACTION: Etuvetidigene autotemcel is prepared from apheresed cells that are transduced with a replication defective, self-inactivating HIV-based lentiviral vector. Antiretrovirals may interfere with the manufacturing of the apheresed cells.

CLINICAL EFFECTS: Use of antiretrovirals before mobilization and apheresis may interfere with the production of etuvetidigene autotemcel.(1)

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: Patients should not take antiretrovirals for at least one month prior to mobilization and until at least 7 days after etuvetidigene autotemcel infusion.(1) If a patient requires antiretroviral agents for HIV post-exposure prophylaxis, etuvetidigene autotemcel treatment should be delayed until HIV testing is negative at 6 months post-exposure.(1)

DISCUSSION: Antiretroviral medications may interfere with the manufacturing of etuvetidigene autotemcel therapy.(1)

Anti-Retrovirals/Lovotibeglogene Autotemcel

SEVERITY LEVEL: 1-Contraindicated Drug Combination: This drug combination is contraindicated and generally should not be dispensed or administered to the same patient.

MECHANISM OF ACTION: Lovotibeglogene autotemcel is prepared from apheresed cells that are transduced with a replication defective, self-inactivating lentiviral vector. Antiretrovirals may interfere with the manufacturing of apheresed cells.

CLINICAL EFFECTS: Use of antiretrovirals before mobilization and apheresis may interfere with the production of lovotibeglogene autotemcel.(1)

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: Discontinue antiretrovirals for at least one month prior to mobilization and until all cycles of apheresis are completed.(1) There are some long-acting antiretroviral medications that may require a longer duration of discontinuation for elimination of the medication. If a patient is taking anti-retrovirals for HIV prophylaxis, confirm a negative test for HIV before beginning mobilization and apheresis of CD34+ cells.(1)

DISCUSSION: Antiretroviral medications may interfere with the manufacturing of lovotibeglogene autotemcel therapy.(1)

Anti-Retrovirals; Hydroxyurea/Betibeglogene Autotemcel

SEVERITY LEVEL: 1-Contraindicated Drug Combination: This drug combination is contraindicated and generally should not be dispensed or administered to the same patient.

MECHANISM OF ACTION: Betibeglogene autotemcel is prepared from apheresed cells that are transduced with a replication defective, self-inactivating lentiviral vector. Antiretrovirals may interfere with the manufacturing of apheresed cells. Hydroxyurea may interfere with hematopoietic stem cell (HSC) mobilization of CD34+ cells.(1)

CLINICAL EFFECTS: Use of hydroxyurea before mobilization may result in unsuccessful stem cell mobilization. Use of antiretrovirals before mobilization and apheresis may interfere with the production of betibeglogene autotemcel.

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: Discontinue antiretrovirals and hydroxyurea for at least one month prior to mobilization and until all cycles of apheresis are completed. If a patient requires antiretrovirals for HIV prophylaxis, then confirm a negative HIV test before beginning mobilization and apheresis of CD34+ cells.

DISCUSSION: Antiretroviral medications and hydroxyurea may interfere with the manufacturing of betibeglogene autotemcel therapy.(1)

Bcrp Inhibitors/Topotecan

SEVERITY LEVEL: 1-Contraindicated Drug Combination: This drug combination is contraindicated and generally should not be dispensed or administered to the same patient.

MECHANISM OF ACTION: Inhibitors of the BCRP transporter may increase the intestinal absorption and hepatic uptake of topotecan.(1)

CLINICAL EFFECTS: The concurrent administration of topotecan with an inhibitor of BCRP may result in elevated levels of topotecan and signs of toxicity. These signs may include but are not limited to anemia, diarrhea, and thrombocytopenia.(1)

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: The US manufacturer of topotecan states that the use of topotecan and BCRP inhibitors should be avoided. If concurrent use is warranted, carefully monitor patients for adverse effects.(1)

DISCUSSION: In clinical studies, the combined use of elacridar (100 mg to 1000 mg), a BCRP and P-gp inhibitor, increased the area-under-curve (AUC) of topotecan approximately 2.5-fold.(1) BCRP inhibitors linked to this monograph include: capmatinib, clopidogrel, curcumin, danicopan, dasabuvir, elbasvir, enasidenib, ensitrelvir, febuxostat, fostamatinib, fostemsavir, glecaprevir, grazoprevir, lazertinib, oteseconazole, pacritinib, paritaprevir, pibrentasvir, pirtobrutinib, regorafenib, resmetirom, ritonavir, roxadustat, tafamidis, ticagrelor, tolvaptan, turmeric, vadadustat, velpatasvir, voxilaprevir, and zongertinib.(2,3)

Fostemsavir/Ethinyl Estradiol (> 30 Mcg)

SEVERITY LEVEL: 1-Contraindicated Drug Combination: This drug combination is contraindicated and generally should not be dispensed or administered to the same patient.

MECHANISM OF ACTION: The mechanism of action has not been described.

CLINICAL EFFECTS: Coadministration of ethinyl estradiol and fostemsavir may increase the plasma concentrations and toxicities of ethinyl estradiol.(1)

PREDISPOSING FACTORS: Patients with risk factors for thrombosis may be at higher risk of adverse events, including those with advanced age, obesity (BMI >30), smoking, prolonged immobilization, heart failure, hypercoagulable states, history of venous thromboembolism, malignancy, and major surgery.

PATIENT MANAGEMENT: The manufacturer of fostemsavir states that the daily dose of ethinyl estradiol should not exceed 30 mcg when used in patients concurrently on fostemsavir.(1)

DISCUSSION: In a study, coadministration of ethinyl estradiol 30 mcg/norethindrone 1.5 mg once daily and fostemsavir 600 mg twice daily increased the area-under-curve (AUC) and maximum concentration (Cmax) of ethinyl estradiol by 1.4-fold and 1.39-fold, respectively. The exposure to norethindrone was not significantly different.(1)

Fostemsavir/Strong Cyp3a4 Inducers

SEVERITY LEVEL: 1-Contraindicated Drug Combination: This drug combination is contraindicated and generally should not be dispensed or administered to the same patient.

MECHANISM OF ACTION: Strong inducers of CYP3A4 may induce the metabolism of fostemsavir via this pathway.(1)

CLINICAL EFFECTS: Concurrent or recent use of strong CYP3A4 inducers may result in reduced plasma levels of fostemsavir, resulting in loss of virologic response.(1)

PREDISPOSING FACTORS: Induction effects may be more likely with regular use of the inducer for longer than 1-2 weeks.

PATIENT MANAGEMENT: The concurrent use of fostemsavir with strong CYP3A4 inducers is contraindicated.(1)

DISCUSSION: In an interaction study of rifampin 600 mg daily (a strong CYP3A4 inducer) and a single 1200 mg dose of fostemsavir, concurrent use decreased fostemsavir concentration maximum (Cmax) by 76% and area-under-curve (AUC) by 82%.(1) Strong CYP3A4 inducers linked to this monograph are: apalutamide, barbiturates, carbamazepine, encorafenib, enzalutamide, fosphenytoin, ivosidenib, lumacaftor, mitotane, phenobarbital, phenytoin, primidone, rifampin, rifapentine and St John's Wort.(2,3)

Oatp1b1-3 Inhibitors/Atrasentan

SEVERITY LEVEL: 1-Contraindicated Drug Combination: This drug combination is contraindicated and generally should not be dispensed or administered to the same patient.

MECHANISM OF ACTION: OATP1B1 and 1B3 inhibitors may increase the absorption and/or decrease the hepatic uptake of atrasentan.(1)

CLINICAL EFFECTS: Concurrent use of OATP1B1 or 1B3 inhibitors may result in elevated levels of and side effects from atrasentan, including fluid retention and hepatotoxicity.(1)

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: The manufacturer of atrasentan states that concurrent use of OATP1B1 or 1B3 inhibitors should be avoided.(1)

DISCUSSION: In a clinical study, atrasentan maximum concentration (Cmax) was 4.3 times higher and area-under-curve (AUC) was 3.8 times higher following coadministration of a single dose of 0.75 mg atrasentan with cyclosporine (OATP1B1 and 1B3 inhibitor) compared to atrasentan alone. OATP1B1 and OATP1B3 inhibitors include: atazanavir, belumosudil, boceprevir, clarithromycin, cobicistat, cyclosporine, eltrombopag, erythromycin, fostemsavir, gemfibrozil, glecaprevir-pibrentasvir, leflunomide, leniolisib, letermovir, lopinavir, nirmatrelvir, ombitasvir-paritaprevir, resmetirom, ritonavir, roxadustat, saquinavir, simeprevir, telaprevir, teriflunomide, tipranavir, vadadustat, velpatasvir, voclosporin, and voxilaprevir.(1,2)

Oatp1b1-3 Inhibitors/Elbasvir-Grazoprevir

SEVERITY LEVEL: 1-Contraindicated Drug Combination: This drug combination is contraindicated and generally should not be dispensed or administered to the same patient.

MECHANISM OF ACTION: Inhibitors of OATP1B1/3 may decrease the hepatocyte uptake and increase the plasma concentrations of elbasvir and grazoprevir.(1-3)

CLINICAL EFFECTS: Concurrent use of an inhibitor of OATP1B1/3 may result in elevated levels of grazoprevir and an increased risk of ALT elevations.(1-3)

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: Concurrent use of elbasvir-grazoprevir and OATP1B1/3 inhibitors is contraindicated.(1-2,4) If concurrent use is deemed medically necessary, monitor the patient for toxicity and elevated AST levels.

DISCUSSION: In a study in 10 subjects, atazanavir/ritonavir (300/100 mg daily) increased the maximum concentration (Cmax), area-under-curve (AUC), and minimum concentration (Cmin) of elbasvir (50 mg daily) by 4.15-fold, 4.76-fold, and 6.45-fold, respectively. There were no clinically significant effects on atazanavir levels.(1,2) In a study in 12 subjects, atazanavir/ritonavir (300/100 mg daily) increased the Cmax, AUC, and Cmin of grazoprevir (200 mg daily) by 6.24-fold, 10.58-fold, and 11.64-fold, respectively. There were no clinically significant effects on atazanavir levels.(1,2) In a study in 14 subjects, cyclosporine (400 mg single dose) increased the Cmax, AUC, and Cmin of elbasvir (50 mg daily) by 1.95-fold, 1.98-fold, and 2.21-fold, respectively. The Cmax, AUC, and Cmin of grazoprevir (200 mg daily) increased by 17-fold, 15.21-fold, and 3.39-fold, respectively. There were no clinically significant effects on cyclosporine levels.(1,2) In a study in 10 subjects, darunavir/ritonavir (600/100 mg twice daily) increased the Cmax, AUC, and Cmin of elbasvir (50 mg daily) by 1.67-fold, 1.66-fold, and 1.82-fold, respectively. There were no clinically significant effects on darunavir levels.(1,2) In a study in 13 subjects, darunavir/ritonavir (600/100 mg twice daily) increased the Cmax, AUC, and Cmin of grazoprevir (200 mg daily) by 5.27-fold, 7.50-fold, and 8.05-fold, respectively. There were no clinically significant effects on darunavir levels.(1,2) In a study in 10 subjects, lopinavir/ritonavir (400/100 mg twice daily) increased the Cmax, AUC, and Cmin of elbasvir (50 mg daily) by 2.87-fold, 3.71-fold, and 4.58-fold, respectively. There were no clinically significant effects on lopinavir levels.(1,2) In a study in 13 subjects, lopinavir/ritonavir (400/100 mg twice daily) increased the Cmax, AUC, and Cmin of grazoprevir (200 mg daily) by 7.31-fold, 12.86-fold, and 21.70-fold, respectively. There were no clinically significant effects on lopinavir levels.(1,2) In single dose studies, rifampin increased levels of both elbasvir and grazoprevir. In a study in 14 subjects, rifampin (600 mg single IV dose) increased the Cmax, AUC, and Cmin of a single dose of elbasvir (50 mg) by 41%, 22%, and 31%, respectively. In a study in 14 subjects, rifampin (600 mg single oral dose) increased the Cmax, AUC, and Cmin of a single dose of elbasvir (50 mg) by 29%, 17%, and 21%, respectively. In a study in 12 subjects, rifampin (600 mg single IV dose) increased the Cmax, AUC, and Cmin of a single dose of grazoprevir (200 mg) by 10.94-fold, 10.21-fold, and 1.77-fold, respectively. In a study in 12 subjects, rifampin (600 mg single oral dose) increased the Cmax, AUC, and Cmin of a single dose of grazoprevir (200 mg) by 6.52-fold, 8.35-fold, and 1.61-fold, respectively.(1) OATP1B1/3 inhibitors include: atazanavir, belumosudil, cyclosporine, darunavir, fostemsavir, leniolisib, letermovir, lopinavir, nirmatrelvir/ritonavir, paritaprevir, resmetirom, roxadustat, saquinavir, tipranavir, vadadustat, and voclosporin.(1-3)

Oatp1b3 Inhibitors/Zavegepant

SEVERITY LEVEL: 1-Contraindicated Drug Combination: This drug combination is contraindicated and generally should not be dispensed or administered to the same patient.

MECHANISM OF ACTION: Zavegepant is a substrate of the organic anion transporting polypeptide 1B3 (OATP1B3) transporter. Inhibitors of OATP1B3 may increase zavegepant exposure.(1)

CLINICAL EFFECTS: Concurrent use of OATP1B3 inhibitors may result in increased levels of and toxicity from zavegepant.(1)

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: Concurrent administration of zavegepant with OATP1B3 inhibitors should be avoided.(1)

DISCUSSION: In a study, rifampin (an OATP1B3 and NTCP inhibitor) at steady state increased the area-under-curve (AUC) and maximum concentration (Cmax) of zavegepant by 2.3-fold and 2.2-fold. Since rifampin is also a CYP3A4 inducer and zavegepant is metabolized by CYP3A4, concurrent use of zavegepant with other OATP1B3 inhibitors that are not CYP3A4 inducers may have an even more significant effect on zavegepant exposure.(1) OATP1B3 inhibitors include: atazanavir, belumosudil, cobicistat, cyclosporine, darolutamide, enasidenib, encorafenib, fostemsavir, glecaprevir/pibrentasvir, leflunomide, leniolisib, letermovir, lopinavir/ritonavir, paritaprevir, resmetirom, rifampin, ritonavir, teriflunomide, velpatasvir, voclosporin, and voxilaprevir.(2-9)

P-Gp Or Bcrp Inhibitors/Ubrogepant (> 50 Mg)

SEVERITY LEVEL: 1-Contraindicated Drug Combination: This drug combination is contraindicated and generally should not be dispensed or administered to the same patient.

MECHANISM OF ACTION: Inhibitors of P-glycoprotein (P-gp) or BCRP may increase the absorption of ubrogepant.(1)

CLINICAL EFFECTS: The concurrent administration of ubrogepant with an inhibitor of P-glycoprotein or BCRP may result in elevated levels of ubrogepant.(1)

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: The manufacturer recommends a dosage adjustment of ubrogepant when coadministered with P-gp or BCRP inhibitors. The dose of ubrogepant should not exceed 50 mg for initial dose. If a second dose of ubrogepant is needed, the dose should not exceed 50 mg.(1) For patients on concurrent therapy with vimseltinib and ubrogepant: the manufacturer of vimseltinib states concurrent use with P-gp substrates should be avoided. If concurrent use cannot be avoided, take vimseltinib at least 4 hours prior to ubrogepant.(3) For patients on daraxonrasib, the manufacturer of daraxonrasib states that it should be taken at least 4 hours apart from P-gp substrates.(4)

DISCUSSION: Ubrogepant is a substrate of P-gp and BCRP transporters. Use of P-gp or BCRP inhibitors may increase the exposure of ubrogepant. Clinical drug interaction studies with inhibitors of these transporters were not conducted. The US manufacturer of ubrogepant recommends dose adjustment if ubrogepant is coadministered with P-gp or BCRP inhibitors.(1) BCRP inhibitors linked to this monograph include: belumosudil, clopidogrel, curcumin, eltrombopag, febuxostat, fostemsavir, leniolisib, momelotinib, oteseconazole, regorafenib, resmetirom, ritonavir, rolapitant, roxadustat, tafamidis, oral tedizolid, turmeric, vadadustat, and zongertinib.(2,3,5) P-glycoprotein inhibitors linked to this monograph include: asunaprevir, belumosudil, capmatinib, carvedilol, danicopan, daraxonrasib, daridorexant, imlunestrant, neratinib, osimertinib, propafenone, quinidine, selpercatinib, sofosbuvir/velpatasvir/voxilaprevir, tepotinib, valbenazine, vimseltinib, and voclosporin.(2,3,5)

Select Bcrp Inhibitors/Aumolertinib

SEVERITY LEVEL: 1-Contraindicated Drug Combination: This drug combination is contraindicated and generally should not be dispensed or administered to the same patient.

MECHANISM OF ACTION: Aumolertinib is a substrate for BCRP. Inhibitors of the BCRP transporter may increase the intestinal absorption and decrease hepatic elimination of aumolertinib.(1)

CLINICAL EFFECTS: Concurrent use with selected BCRP inhibitors may result in higher systemic concentrations of aumolertinib, which may increase the risk for cardiac failure, rhabdomyolysis, thrombosis, elevated LFTs, hyponatremia, hematologic toxicity, and QT prolongation, which may result in potentially life-threatening cardiac arrhythmias like torsade de pointes (TdP).(1)

PREDISPOSING FACTORS: The risk of QT prolongation or torsades de pointes may be increased in patients with cardiovascular disease (e.g. heart failure, myocardial infarction, history of torsades de pointes, congenital long QT syndrome), hypokalemia, hypomagnesemia, hypocalcemia, bradycardia, female gender, or advanced age.(2) Concurrent use of more than one drug known to cause QT prolongation or higher systemic concentrations of either QT prolonging drug are additional risk factors for torsades de pointes. Factors which may increase systemic drug concentrations include rapid infusion of an intravenous dose or impaired metabolism or elimination of the drug (e.g. coadministration with an agent which inhibits its metabolism or elimination, genetic impairment in drug metabolism or elimination, and/or renal/hepatic dysfunction).(2) Patients with risk factors for thrombosis may be at higher risk of adverse events, including those with advanced age, obesity (BMI >30), smoking, prolonged immobilization, heart failure, hypercoagulable state, history of venous thromboembolism, malignancy, and major surgery. The risk for rhabdomyolysis may be greater in patients 65 years and older, inadequately treated hypothyroidism, renal impairment, carnitine deficiency, malignant hyperthermia, or in patients with a history of rhabdomyolysis.

PATIENT MANAGEMENT: The manufacturer of aumolertinib states concomitant administration of aumolertinib should be avoided with BCRP inhibitors.(1) If concurrent therapy is warranted, consider obtaining serum calcium, magnesium, and potassium levels and monitoring ECG at baseline and at regular intervals. Correct any electrolyte abnormalities. Instruct patients to report any irregular heartbeat, dizziness, or fainting.

DISCUSSION: Based on in vitro data, aumolertinib is a substrate of BCRP.(1) BCRP inhibitors linked to this monograph include: asciminib, clopidogrel, darolutamide, elbasvir/grazoprevir, eltrombopag, enasidenib, febuxostat, fostemsavir, lazertinib, leniolisib, momelotinib, oteseconazole, regorafenib, rolapitant, roxadustat, tafamidis, ticagrelor, vadadustat, and zongertinib.(3,4)

Selected Inhibitors Of P-Gp Or Bcrp/Pazopanib

SEVERITY LEVEL: 1-Contraindicated Drug Combination: This drug combination is contraindicated and generally should not be dispensed or administered to the same patient.

MECHANISM OF ACTION: Inhibitors of P-glycoprotein (P-gp) or BCRP may increase the absorption of pazopanib.(1)

CLINICAL EFFECTS: The concurrent administration of pazopanib with an inhibitor of P-glycoprotein or BCRP may result in elevated levels of pazopanib and signs of toxicity.(1)

PREDISPOSING FACTORS: The risk of QT prolongation or torsade de pointes may be increased in patients with cardiovascular disease (e.g. heart failure, myocardial infarction, history of torsade de pointes, congenital long QT syndrome), hypokalemia, hypomagnesemia, hypocalcemia, bradycardia, female gender, or advanced age.(2) Concurrent use of more than one drug known to cause QT prolongation or higher systemic concentrations of either QT prolonging drug are additional risk factors for torsade de pointes. Factors which may increase systemic drug concentrations include rapid infusion of an intravenous dose or impaired metabolism or elimination of the drug (e.g. coadministration with an agent which inhibits its metabolism or elimination, and/or renal/hepatic dysfunction).(2)

PATIENT MANAGEMENT: The US manufacturer of pazopanib states concurrent use of P-gp inhibitors or BCRP inhibitors should be avoided.(1) Monitor patients for increased side effects from pazopanib. The manufacturer of daraxonrasib states P-gp substrates should be administered at least 4 hours apart from daraxonrasib.(5) If concurrent therapy is warranted, consider obtaining serum calcium, magnesium, and potassium levels and monitoring ECG at baseline and at regular intervals. Correct any electrolyte abnormalities. Instruct patients to report any irregular heartbeat, dizziness, or fainting.

DISCUSSION: Pazopanib is a substrate of P-gp and BCRP. Inhibitors of these transporters are expected to increase pazopanib levels.(1) BCRP inhibitors linked to this monograph include: asciminib, belumosudil, clopidogrel, cyclosporine, curcumin, darolutamide, eltrombopag, enasidenib, febuxostat, fostemsavir, grazoprevir, lazertinib, leflunomide, leniolisib, momelotinib, oteseconazole, pirtobrutinib, regorafenib, resmetirom, ritonavir, rolapitant, roxadustat, tafamidis, teriflunomide, tolvaptan, turmeric, vadadustat, and zongertinib.(1,3-5) P-glycoprotein inhibitors linked to this monograph include: asunaprevir, belumosudil, capmatinib, carvedilol, cyclosporine, danicopan, daraxonrasib, daridorexant, diltiazem, flibanserin, fostamatinib, ginseng, glecaprevir/pibrentasvir, imlunestrant, isavuconazonium, ivacaftor, ledipasvir, neratinib, sofosbuvir/velpatasvir/voxilaprevir, tepotinib, tezacaftor, ticagrelor, valbenazine, verapamil, vimseltinib, and voclosporin.(3,4)

Severe Interaction: Action is required to reduce the risk of severe adverse interaction.

Anti-Retrovirals/Marnetegragene Autotemcel

SEVERITY LEVEL: 2-Severe Interaction: Action is required to reduce the risk of severe adverse interaction.

MECHANISM OF ACTION: Marnetegragene autotemcel is prepared from apheresed cells that are transduced with a replication defective, self-inactivating lentiviral vector. Antiretrovirals may interfere with the manufacturing of transduced cells.

CLINICAL EFFECTS: Use of antiretrovirals before mobilization and apheresis may interfere with the production of marnetegragene autotemcel.

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: Discontinue antiretrovirals for at least one month prior to mobilization (or the expected duration of time needed for elimination of the antiretrovirals) until all cycles of apheresis are completed. If a patient requires antiretrovirals for HIV prophylaxis, then confirm a negative HIV test before beginning mobilization and apheresis of CD34+ cells.(1)

DISCUSSION: Antiretroviral medications may interfere with the manufacturing of marnetegragene autotemcel.(1)

Oatp1b1-3 Inhibitors/Brincidofovir

SEVERITY LEVEL: 2-Severe Interaction: Action is required to reduce the risk of severe adverse interaction.

MECHANISM OF ACTION: OATP1B1 and 1B3 inhibitors may increase the absorption and/or decrease the hepatic uptake of brincidofovir.(1)

CLINICAL EFFECTS: Concurrent use of OATP1B1 or 1B3 inhibitors may result in elevated levels of and side effects from brincidofovir.(1)

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: The manufacturer of brincidofovir states that alternative medications that are not OATP1B1 or 1B3 inhibitors should be considered. If concurrent use is necessary, instruct the patient to take the OATP1B1 or 1B3 inhibitor at least 3 hours after brincidofovir and increase monitoring for side effects, including transaminase and bilirubin elevations and GI side effects like diarrhea.(1)

DISCUSSION: In a clinical trial, single-dose oral cyclosporine (600 mg, an OATP1B1 and 1B3 inhibitor) increased the mean brincidofovir area-under-curve (AUC) and maximum concentration (Cmax) by 374% and 269%, respectively.(1) OATP1B1 and 1B3 inhibitors include: atazanavir, belumosudil, boceprevir, clarithromycin, cyclosporine, darunavir, eltrombopag, encorafenib, erythromycin, gemfibrozil, glecaprevir-pibrentasvir, ledipasvir, leflunomide, leniolisib, letermovir, lopinavir, ombitasvir-paritaprevir, paritaprevir, resmetirom, rifampin, ritonavir, roxadustat, saquinavir, simeprevir, sofosbuvir, telaprevir, teriflunomide, tipranavir, vadadustat, velpatasvir, and voclosporin.(1,2)

Selected Inhibitors Of Bcrp/Cladribine Oral

SEVERITY LEVEL: 2-Severe Interaction: Action is required to reduce the risk of severe adverse interaction.

MECHANISM OF ACTION: Inhibitors of BCRP may increase the absorption of cladribine.(1-2)

CLINICAL EFFECTS: The concurrent administration of cladribine with an inhibitor of BCRP may result in elevated levels of cladribine and signs of toxicity.(1-2)

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: The manufacturer of cladribine states concurrent use of BCRP inhibitors should be avoided during the 4- to 5-day cladribine treatment.(1-2) Selection of an alternative concurrent medication with no or minimal transporter inhibiting proprieties should be considered. If this is not possible, dose reduction to the minimum mandatory dose of the BCRP inhibitor, separation in timing of administration, and careful patient monitoring is recommended.(1-2) Monitor for signs of hematologic toxicity. Lymphocyte counts should be monitored.

DISCUSSION: Cladribine is a substrate of BCRP. Inhibitors of this transporter are expected to increase cladribine levels.(1-2) BCRP inhibitors linked to this monograph include: capmatinib, clopidogrel, curcumin, danicopan, darolutamide, dasabuvir, eltrombopag, enasidenib, ensitrelvir, febuxostat, fostamatinib, fostemsavir, glecaprevir/pibrentasvir, grazoprevir, lazertinib, oteseconazole, pacritinib, paritaprevir, regorafenib, resmetirom, ritonavir, rolapitant, roxadustat, selpercatinib, sofosbuvir/velpatasvir/voxilaprevir, tafamidis, ticagrelor, tolvaptan, turmeric, vadadustat, and zongertinib.(1-4)

Selected Oatp1b1-3 Inhibitors/Voxilaprevir

SEVERITY LEVEL: 2-Severe Interaction: Action is required to reduce the risk of severe adverse interaction.

MECHANISM OF ACTION: OATP1B1 and OATP1B3 inhibitors may increase exposure to voxilaprevir.(1)

CLINICAL EFFECTS: Concurrent use of OATP1B1 and OATP1B3 inhibitors may result in increased levels of and toxicity from voxilaprevir.(1)

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: Concurrent administration of voxilaprevir with OATP1B1 and OATP1B3 inhibitors is not recommended.(1,4) If concurrent therapy is warranted, monitor patients for adverse effects. The American Society of Transplantation guidelines state that the combination of voxilaprevir and cyclosporine is contraindicated.(3)

DISCUSSION: In a study in 25 subjects, cyclosporine (600 mg single dose) increased the maximum concentration (Cmax) and area-under-curve (AUC) of voxilaprevir (100 mg single dose) by 19.02-fold and 9.39-fold, respectively. There were no significant effects on cyclosporine levels.(1) OATP inhibitors include: atazanavir, belumosudil, cyclosporine, encorafenib, fostemsavir, leniolisib, letermovir, lopinavir, paritaprevir, resmetirom, roxadustat, vadadustat, and voclosporin.(1,2,4)

Moderate Interaction: Assess the risk to the patient and take action as needed.

Fostemsavir/Ethinyl Estradiol (<= 30 Mcg)

SEVERITY LEVEL: 3-Moderate Interaction: Assess the risk to the patient and take action as needed.

MECHANISM OF ACTION: The mechanism of action has not been described.

CLINICAL EFFECTS: Coadministration of ethinyl estradiol and fostemsavir may increase the plasma concentrations and toxicities of ethinyl estradiol.(1)

PREDISPOSING FACTORS: Patients with risk factors for thrombosis may be at higher risk of adverse events, including those with advanced age, obesity (BMI >30), smoking, prolonged immobilization, heart failure, hypercoagulable states, history of venous thromboembolism, malignancy, and major surgery.

PATIENT MANAGEMENT: The manufacturer of fostemsavir states that the daily dose of ethinyl estradiol should not exceed 30 mcg when used in patients concurrently on fostemsavir.(1)

DISCUSSION: In a study, coadministration of ethinyl estradiol 30 mcg/norethindrone 1.5 mg once daily and fostemsavir 600 mg twice daily increased the area-under-curve (AUC) and maximum concentration (Cmax) of ethinyl estradiol by 1.4-fold and 1.39-fold, respectively. The exposure to norethindrone was not significantly different.(1)

Fostemsavir/Selected Hmg-Coa Reductase Inhibitors

SEVERITY LEVEL: 3-Moderate Interaction: Assess the risk to the patient and take action as needed.

MECHANISM OF ACTION: Fostemsavir may inhibit OATP1B1 and OATP1B3, resulting in decreased hepatocyte uptake and increased plasma concentrations of atorvastatin, fluvastatin, pitavastatin, rosuvastatin, and simvastatin.(1)

CLINICAL EFFECTS: Concurrent use of fostemsavir may result in elevated levels of and toxicity from atorvastatin, fluvastatin, pitavastatin, rosuvastatin, or simvastatin, including rhabdomyolysis.(1)

PREDISPOSING FACTORS: The risk for myopathy or rhabdomyolysis may be greater in patients 65 years and older, inadequately treated hypothyroidism, renal impairment, carnitine deficiency, malignant hyperthermia, or in patients with a history of myopathy or rhabdomyolysis. Patients with a SLCO1B1 polymorphism that leads to decreased function of the hepatic uptake transporter OATP1B1 may have increased statin concentrations and be predisposed to myopathy or rhabdomyolysis. Patients on fluvastatin who are CYP2C9 intermediate or poor metabolizers may have increased fluvastatin concentrations and risk of myopathy. Patients on rosuvastatin with ABCG2 polymorphisms leading to decreased or poor BCRP transporter function may have increased rosuvastatin concentrations and risk of myopathy.

PATIENT MANAGEMENT: The manufacturer of fostemsavir states that the lowest possible starting dose of statins should be used. Patients should be monitored for statin-associated adverse events.(1)

DISCUSSION: In a study, fostemsavir 600 mg twice daily increased the area-under-curve (AUC) and maximum concentration (Cmax) of single-dose rosuvastatin 10 mg by 1.69-fold and 1.78-fold, respectively.(1)

Oatp1b1-3 Inhibitors/Momelotinib

SEVERITY LEVEL: 3-Moderate Interaction: Assess the risk to the patient and take action as needed.

MECHANISM OF ACTION: OATP1B1 and 1B3 inhibitors may decrease the hepatic uptake of momelotinib.(1)

CLINICAL EFFECTS: Concurrent use of OATP1B1 and 1B3 inhibitors may result in elevated levels of and side effects from momelotinib, including myelosuppression and hepatotoxicity.(1)

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: Concurrent use of momelotinib with OATP1B1 and 1B3 inhibitors should be approached with caution. Monitor patients closely for adverse reactions and consider dose modifications per momelotinib prescribing recommendations.(1)

DISCUSSION: Concurrent administration of a single dose rifampin, an OATP1B1/1B3 inhibitor, increased the maximum concentration (Cmax) and area-under-curve (AUC) of a single dose of momelotinib by 40% and 57%, respectively. The M21 metabolite Cmax increased 6% and AUC increased 12%.(1) OATP1B1 inhibitors include: atazanavir, belumosudil, boceprevir, cobicistat, cyclosporine, darolutamide, darunavir, eltrombopag, enasidenib, encorafenib, erythromycin, fostemsavir, gemfibrozil, glecaprevir-pibrentasvir, ledipasvir, letermovir, lopinavir, nirmatrelvir, paritaprevir, resmetirom, rifampin, roxadustat, saquinavir, simeprevir, telaprevir, tipranavir, vadadustat, velpatasvir, and voclosporin.(1,2)

P-Gp Or Bcrp Inhibitors/Ubrogepant (<= 50 Mg)

SEVERITY LEVEL: 3-Moderate Interaction: Assess the risk to the patient and take action as needed.

MECHANISM OF ACTION: Inhibitors of P-glycoprotein (P-gp) or BCRP may increase the absorption of ubrogepant.(1)

CLINICAL EFFECTS: The concurrent administration of ubrogepant with an inhibitor of P-glycoprotein or BCRP may result in elevated levels of ubrogepant.(1)

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: The manufacturer recommends a dosage adjustment of ubrogepant when coadministered with P-gp or BCRP inhibitors. The dose of ubrogepant should not exceed 50 mg for initial dose. If a second dose of ubrogepant is needed, the dose should not exceed 50 mg.(1) For patients on concurrent therapy with vimseltinib and ubrogepant: The manufacturer of vimseltinib states concurrent use with P-gp substrates should be avoided. If concurrent use cannot be avoided, take vimseltinib at least 4 hours prior to ubrogepant.(3) For patients on daraxonrasib, the manufacturer of daraxonrasib states that it should be taken at least 4 hours apart from P-gp substrates.(4)

DISCUSSION: Ubrogepant is a substrate of P-gp and BCRP transporters. Use of P-gp or BCRP inhibitors may increase the exposure of ubrogepant. Clinical drug interaction studies with inhibitors of these transporters were not conducted. The US manufacturer of ubrogepant recommends dose adjustment if ubrogepant is coadministered with P-gp or BCRP inhibitors.(1) BCRP inhibitors linked to this monograph include: belumosudil, clopidogrel, curcumin, eltrombopag, febuxostat, fostemsavir, leniolisib, momelotinib, oteseconazole, regorafenib, resmetirom, ritonavir, rolapitant, roxadustat, tafamidis, oral tedizolid, turmeric, vadadustat, and zongertinib.(2,3,5,6) P-glycoprotein inhibitors linked to this monograph include: asunaprevir, belumosudil, capmatinib, carvedilol, danicopan, daraxonrasib, daridorexant, imlunestrant, neratinib, osimertinib, propafenone, quinidine, selpercatinib, sofosbuvir/velpatasvir/voxilaprevir, tepotinib, valbenazine, vimseltinib, and voclosporin.(2,3,5,6)

*Hypersensitivity to fostemsavir or any of the components of the formulation.

*Coadministration with strong cytochrome P-450 (CYP) 3A inducers.

There are no contraindication contraindications for this drug.

• Chronic hepatitis B
• Chronic hepatitis C

There are no moderate contraindications for this drug.

The most common adverse effect (all grades) observed in >=5% of patients receiving fostemsavir was nausea.

Less Frequent

• Abnormal hepatic function tests
• Hyperbilirubinemia
• Hyperglycemia
• Increased alanine transaminase
• Increased aspartate transaminase

Rare or Very Rare

• Atypical mycobacterial infection
• Cytomegalovirus disease
• Graves' disease
• Guillain-barre syndrome
• Pneumocystis jirovecii pneumonia
• Polymyositis
• Prolonged QT interval

More Frequent

• Nausea

Less Frequent

• Acute abdominal pain
• Diarrhea
• Drowsy
• Dyspepsia
• Fatigue
• Headache disorder
• Skin rash
• Sleep disorder
• Vomiting

Rare or Very Rare

• Dizziness
• Myalgia
• Peripheral sensory neuropathy
• Pruritus of skin

No enhanced messaging available.

The safety and effectiveness of fostemsavir have not been established in pediatric patients.

There is a pregnancy exposure registry that monitors pregnancy outcomes in individuals exposed to fostemsavir during pregnancy. Healthcare providers are encouraged to register patients by calling the Antiretroviral Pregnancy Registry (APR) at 1-800-258-4263or https://www.apregistry.com.

There are insufficient human data on the use of fostemsavir in pregnant patients to adequately assess a drug-associated risk of birth defects and miscarriage. In animal studies, administration of fostemsavir during organogenesis resulted in no adverse developmental effects at clinically relevant temsavir exposures.

It is not known whether fostemsavir is present in human breast milk, affects milk production, or has effects on the breastfed infant. When administered to lactating rats, fostemsavir-related drug was present in rat milk at concentrations similar to those in maternal plasma. When a drug is present in animal milk, it is likely to be present in human milk.

The HHS perinatal HIV transmission guideline provides updated recommendations on infant feeding. The guideline states that patients with HIV should receive evidence-based, patient-centered counseling to support shared decision making about infant feeding. During counseling, patients should be informed that feeding with appropriate formula or pasteurized donor human milk from a milk bank eliminates the risk of postnatal HIV transmission to the infant. Additionally, achieving and maintaining viral suppression with antiretroviral therapy during pregnancy and postpartum reduces the risk of breastfeeding HIV transmission to <1%, but does not completely eliminate the risk. Replacement feeding with formula or banked pasteurized donor milk is recommended when patients with HIV are not on antiretroviral therapy and/or do not have a suppressed viral load during pregnancy (at a minimum throughout the third trimester), as well as at delivery.

While there are no specific dosage recommendations for geriatric patients, use caution during administration of fostemsavir due to the greater frequency of renal, hepatic, and cardiac dysfunction in these patients, as well as concomitant diseases and other drug therapy.

Clinical trials of fostemsavir did not include sufficient numbers of patients 65 years of age and older to determine whether they respond differently from younger adults. In general, caution should be exercised in administration of fostemsavir in elderly patients reflecting greater frequency of decreased hepatic, renal, or cardiac function, and of concomitant disease or other drug therapy. Geriatric patients may be more susceptible to drug-induced QT-interval prolongation.