Alternative Dosing Scheme of Pomalidomide 4 mg Every Other Day Versus Pomalidomide 2 mg and 4 mg Every Day; the POMAlternative Study

Pomalidomide either as single therapy or in combination with cyclophosphamide, elotuzumab, bortezomib, or daratumumab are effective treatment regimens in relapsed refractory multiple myeloma (RRMM). Standard dosing is 4 mg/day during 21 days of a 28-day cycle (21/28). However, a clear dose-response association for pomalidomide in patients with multiple myeloma (MM) is lacking. There is data supporting that a dose of 2 mg/day continuously (28/28) induces fewer side effects while efficacy is preserved, compared to 4 mg/day continuously. The response in patients who received pomalidomide 2 mg per day compared to 4 mg per day was higher, with a longer duration of response. In addition, a randomized phase II study showed no difference in efficacy between 4 mg (21/28) and 4 mg continuously. These clinical studies support that a dosage of pomalidomide of 2 mg (28/28) is at least comparable with a dosage of 4 mg (21/28). It is not known if 4 mg every other day (EOD) is comparable to a dosage of pomalidomide 2 mg (28/28) or 4 mg every day (QD, 21/28). For cost reasons, this is interesting as the costs of pomalidomide 4 mg and 2 mg are comparable. Therefore, from a patient and societal perspective, the investigators want to explore if an alternative scheme would be possible by performing a PKPD bio-equivalence pilot study.

Pomalidomide either as single therapy or in combination with cyclophosphamide, elotuzumab, bortezomib, or daratumumab are effective treatment regimens in relapsed refractory multiple myeloma (RRMM). Standard dosing is 4 mg/day during 21 days of a 28-day cycle (21/28). However, a clear dose-response association for pomalidomide in patients with multiple myeloma (MM) is lacking. There is data supporting that a dose of 2 mg/day continuously (28/28) induces fewer side effects while efficacy is preserved, compared to 4 mg/day continuously. The response in patients who received pomalidomide 2 mg per day compared to 4 mg per day was higher, with a longer duration of response. In addition, a randomized phase II study showed no difference in efficacy between 4 mg (21/28) and 4 mg continuously. These clinical studies support that a dosage of pomalidomide of 2 mg (28/28) is at least comparable with a dosage of 4 mg (21/28). It is not known if 4 mg every other day (EOD) is comparable to a dosage of pomalidomide 2 mg (28/28) or 4 mg every day (QD, 21/28). For cost reasons, this is interesting as the costs of pomalidomide 4 mg and 2 mg are comparable. Therefore, from a patient and societal perspective, the investigators want to explore if an alternative scheme would be possible by performing a PKPD bio-equivalence pilot study.

Eligibility Criteria:
Inclusion Criteria:

* Patients with relapsed/refractory multiple myeloma, who are eligible for a treatment regimen which contains pomalidomide. Either monotherapy or in combination with bortezomib, daratumumab, cyclophosphamide, or elotuzumab
* Patients who received a minimum of two cycles of pomalidomide 4mg every day on day 1-21/28
* Age \> 18 years
* WHO performance status 0-3
* Written informed consent

Exclusion Criteria:

* Usage of CYP1A2 inhibitors (e.g. ciprofloxacin, enoxacin, ketoconazole, carbamazepine, fluvoxamine, and grapefruit juice)
* Renal insufficiency requiring dialysis
* Significant hepatic dysfunction (total bilirubin \> 330 μmol/l or transaminases \> 3 times normal level)
* Current smoker
* Hemoglobin \<6.5 mmol/L
* Thrombocytes \<100 \*10\^9/L
* Neutrophiles \<1.5 \*10\^9/L
* Pregnant patients
* Female patients who are able to get pregnant and who do not agree to adequate birth control or complete abstinence
* Male patients who do not agree to adequate birth control or complete abstinence
* Hypersensitivity to pomalidomide or constituents