Immunotherapy in high-risk chemotherapy-resistant patients with metastatic solid tumors and hematological malignancies using intentionally mismatched donor lymphocytes activated with rIL-2: a phase I study

The feasibility and safety of immunotherapy mediated by intentionally mismatched rIL-2 activated killer lymphocytes (IMAK) with no prior stem cell engraftment was investigated in patients with advanced chemotherapy-resistant hematological malignancies and metastatic solid tumors. Our goals were to maximize anti-cancer activity by using intentionally mismatched donor lymphocytes; amplify killing of target cancer cells by rIL-2 activation of killer cells in vitro and in vivo, and avoid the risk of graft-versus-host disease (GVHD) by anticipated rejection of alloreactive donor lymphocytes. Conditioning consisted of 5 days of fludarabine 25 mg/m² or a single dose of cyclophosphamide 1,000 mg/m², 2 subcutaneous injections of alpha interferon (IFN) 3 × 10⁶ and COX2 inhibitors, followed by administration of IMAK (65 ± 5 CD3⁺CD56⁻; 17 ± 5 CD3⁻CD56⁺) in conjunction with low dose subcutaneous rIL-2 (6 × 10⁶ IU/m²/day) for 5 days for continuous activation of alloreactive donor lymphocytes prior to their anticipated rejection. Here, we present our phase 1 clinical study data in a cohort of 40 high-risk patients with metastatic solid tumors and hematological malignancies. Treatment was accompanied by some malaise and occasional self-limited fever but otherwise well tolerated on an outpatient basis. Transient engraftment of donor cells was documented in two patients and only one developed self-limited grade 1 GVHD. Among patients with chemotherapy-resistant disease, long-term progression-free survival was recorded in 5 of 21 evaluable patients with metastatic solid tumors and in four of five patients with hematological malignancies. We conclude that the proposed procedure is feasible, safe, and potentially effective, with some otherwise resistant cancer patients long-term disease-free, thus justifying larger Phase II studies in patients with hematological malignancies and metastatic solid tumors, preferably at a stage of minimal residual disease with the goal in mind to eradicate all malignant cells at an early stage of the disease.