This is a multi-institution, non-randomized, open label, Phase IIa prospective trial to evaluate the safety and tolerability of maintenance lenalidomide after allogeneic hematopoietic stem cell transplantation (HCT).

Lenalidomide maintenance therapy will start between day 60 and 90 after allogeneic HCT at a starting dose of 10mg PO once daily. Dose escalation and de-escalation will be performed depending on tolerability of lenalidomide. Dose range is 5mg every other day to 5 - 25 mg given daily on days 1-21 of a 28-day cycle for 12 cycles maximum or maximum of 12 months from first dose of study drug.

Patients will be followed until 28 days from completing the 12th planned cycle of lenalidomide maintenance or 12 months from first dose of study drug, which ever comes first, (14 to 15 months after receiving the allograft) or discontinuation of study drug.

Inclusion Criteria:

• One prior allograft from an 8/8 or 7/8 allele matched related or unrelated donor, received 60 to 90 days prior to initiation of lenalidomide
• Meet the diagnostic criteria of symptomatic myeloma at anytime prior to allogeneic HCT
• Have high-risk multiple myeloma
• Received ≤ three (3) prior lines of therapy. Prior therapies may include: combination chemotherapy, monotherapy, lenalidomide and autologous HCT. Localized radiation therapy does not count as a single line of therapy. Previous progression on lenalidomide does not exclude participation in the study.
• Received a reduced intensity conditioning regimen
• Received or are receiving a GVHD prophylaxis regimen of a calcineurin inhibitor in combination with either methotrexate, mycophenolate mofetil (MMF) or sirolimus
• Karnofsky performance score ≥ 80 or ECOG ≤ 2
• There must be at least 50% donor chimerism and no evidence of falling donor chimerism within 1 month of enrollment
• Laboratory test results within range, within 14 days prior to initiation of lenalidomide
• All study participants must be registered into the mandatory RevAssist® program, and be willing and able to comply with the requirements of RevAssist®.

Exclusion Criteria:

• Disease progression at time of study entry
• Patients with any grade III-IV GVHD at the time of study entry
• Patients requiring additional immunosuppressive therapy to control acute GVHD other than corticosteroids and immunosuppressive agents used for prophylaxis.
• Concomitant use of other investigational agents
• Patients who have received donor lymphocyte infusions
• Active CNS malignancy
• Uncontrolled bacterial, viral, or fungal infections
• Prior malignancies except resected basal cell carcinoma or treated cervical carcinoma in situ < 5 years from study entry.
• Known hypersensitivity or desquamating rash to either thalidomide or lenalidomide.
• Known positive for HIV or active infectious hepatitis.
• Women who are pregnant or breastfeeding.
• New York Heart Association (NYHA) Class III or IV heart failure, uncontrolled angina, severe uncontrolled ventricular arrhythmias, or electrocardiographic evidence of acute ischemia or active conduction system abnormalities.