Multani, Pratik S.

Background: Although recently available immune-based approaches in multiple myeloma produce high response rates, curative outcomes have not yet been achieved, which highlights the need for new agents that further activate the immune system without increasing toxicity. ORIC-533 is a highly potent and selective, orally bioavailable, small molecule inhibitor of CD73, an enzyme expressed by various cell types, including immune cells and which catalyzes the generation of adenosine from adenosine monophosphate (AMP) (Allard 2019). Adenosine itself is highly immunosuppressive, diminishing activity of a range of immune cell types, including T, NK, and dendritic cells (Young 2014). By blocking adenosine production from AMP via inhibition of CD73, ORIC-533 has demonstrated the ability to restore and enhance immune function. Multiple myeloma (MM) patient bone marrow (BM) contains multiple cell types that also express CD73, including immune cells, cancer-associated fibroblasts, mesenchymal stem cells, and endothelial cells (Allard 2019). Moreover, elevated adenosine levels in the MM BM niche correlate with disease progression (Horenstein 2016; Yang 2020). We have previously observed that CD73-mediated adenosine activity suppresses the cytolytic antitumor immune function in the MM BM milieu (Ray 2022). ORIC-533 treatment reduced adenosine production, overcame this immune suppression with evidence of restored DC-mediated priming and activated cytotoxic CD8 + T-cell function, and significantly enhanced immune cell cytolytic behavior against RRMM tumor cells in autologous patient ex vivo experiments (Junttila 2022), making ORIC-533 a potential immunotherapy for patients with MM. Methods: ORIC-533-01 (NCT05227144) is an ongoing i3+3 Phase 1b dose escalation study in patients with RRMM. The primary objectives are to determine single agent safety/tolerability and pharmacokinetics (PK) of ORIC-533 to select the RP2D. Pharmacodynamic assessments include measurement of CD73 functional activity in serum and BM, as well as enumeration of immune cell subsets and activation state in blood and BM. Patients are also evaluated for clinical efficacy using IMWG criteria. Results: As of 23 June 2023, 17 patients received ORIC-533 once daily across 4 dose levels (400 mg to 1600 mg). All patients were triple-class refractory, 88% were penta-refractory, and 59% also received prior anti-BCMA/CD3 bispecific therapy or anti-BCMA CAR-T therapy. Overall, ORIC-533 was very well tolerated, with 5 patients experiencing a total of 10 treatment-related adverse events (TRAEs). Fatigue was the only G3 AE and the only TRAE seen in more than 1 patient (1 event each of G3 and G2); all other events seen in 1 patient each, were G1 or G2 in severity, and of no specific system organ class. No dose limiting toxicities, no Grade ≥4 TRAEs, and no treatment-related serious adverse events have been observed. PK showed increased exposure with dose with a plasma half-life of ~24 hrs. Soluble CD73 enzymatic activity was nearly completely inhibited by C1D15 in serum of all patients across all dose levels, while the largest relative suppression in surface CD73 activity in BM cells was observed at the highest dose level. There was also evidence for increases in the abundance of circulating NK and CD8+ T cells after 1 treatment cycle, with preliminary evidence of enhanced CD8+ T-cell activation at the highest dose levels tested in both peripheral blood and BM. In addition, early evidence of single agent clinical activity was observed. Conclusions: ORIC-533 has demonstrated an acceptable safety profile and preliminary evidence of immune activation in a heavily pretreated RRMM patient population. Enrollment is ongoing and updated data will be presented.

Purpose: Radioimmunotherapy (RIT) with yttrium-90 (90Y)-labeled anti-CD20 antibody (90Y ibritumomab tiuxetan; Zevalin, IDEC Pharmaceuticals Corporation, San Diego, CA) has a high rate of tumor response in patients with relapsed or refractory, low-grade, follicular, or transformed B-cell non-Hodgkin’s lymphoma (NHL). This study presents the safety data from 349 patients in five studies of outpatient treatment with 90Y ibritumomab tiuxetan. Patients and Methods: Patients received rituximab 250 mg/m2 on days 1 and 8, and either 0.4 mCi/kg (15 MBq/kg) or 0.3 mCi/kg (11 MBq/kg) of 90Y ibritumomab tiuxetan on day 8 (maximum dose, 32 mCi). Patients were observed for up to 4 years after therapy or until progressive disease. Results: Infusion-related toxicities were typically grade 1 or 2 and were associated with rituximab. No significant organ toxicity was noted. Toxicity was primarily hematologic, with nadir counts occurring at 7 to 9 weeks and lasting approximately 1 to 4 weeks depending on the method of calculation. After the 0.4-mCi/kg dose, grade 4 neutropenia, thrombocytopenia, and anemia occurred in 30%, 10%, and 3% of patients, respectively, and after the 0.3-mCi/kg dose, these grade 4 toxicities occurred in 35%, 14%, and 8% of patients, respectively. The risk of hematologic toxicity increased with degree of baseline bone marrow involvement with NHL. Seven percent of patients were hospitalized with infection (3% with neutropenia) and 2% had grade 3 or 4 bleeding events. Myelodysplasia or acute myelogenous leukemia was reported in five patients (1%) 8 to 34 months after treatment. Conclusion: Single-dose 90Y ibritumomab tiuxetan RIT has an acceptable safety profile in relapsed NHL patients with less than 25% lymphoma marrow involvement, adequate marrow reserve, platelets greater than 100,000 cells/μL, and neutrophils greater than 1,500 cells/μL.

PURPOSE: Rituximab is commonly used as a single agent or in combination therapy for non-Hodgkin’s lymphoma (NHL). Ibritumomab tiuxetan radioimmunotherapy targets the same antigen as rituximab and has demonstrated efficacy in rituximab-naïve NHL. This study evaluated ibritumomab tiuxetan in the treatment of rituximab-refractory follicular NHL. PATIENTS AND METHODS: Eligible patients were refractory to rituximab; this was defined as no objective response to rituximab (375 mg/m2 weekly for 4 weeks) or time to progression (TTP) of ≤ 6 months. The ibritumomab tiuxetan treatment regimen consisted of pretreatment with rituximab (250 mg/m2 intravenously on days 1 and 8) to deplete peripheral blood B cells, then yttrium-90 ibritumomab tiuxetan (0.4 mCi/kg; maximum, 32 mCi) intravenously on day 8, administered on an outpatient basis. An imaging/dosimetry dose of indium-111 ibritumomab tiuxetan (5 mCi) was injected after rituximab (day 1) in 28 patients. RESULTS: Fifty-seven patients were treated. The median age was 54 years, 74% had tumors ≥ 5 cm, and all were extensively pretreated (median, four prior therapies; range, one to nine). The estimated radiation-absorbed doses to healthy organs were below the study-defined limit in all patients studied with dosimetry. The overall response rate for the 54 patients with follicular NHL was 74% (15% complete responses and 59% partial responses). The Kaplan-Meier–estimated TTP was 6.8 months (range, 1.1 to ≥ 25.9 months) for all patients and 8.7 months for responders. Adverse events were primarily hematologic; the incidence of grade 4 neutropenia, thrombocytopenia, and anemia was 35%, 9%, and 4%, respectively. CONCLUSION: Ibritumomab tiuxetan radioimmunotherapy is effective in rituximab-refractory patients. The only significant toxicity is hematologic.

Mildly thrombocytopenic patients with relapsed or refractory low-grade non-Hodgkin lymphoma (NHL) have an increased risk of chemotherapy-induced myelosuppression following treatment. The safety and efficacy of radioimmunotherapy with a reduced dose of90Y ibritumomab tiuxetan (0.3 mCi/kg [11 MBq/kg]; maximum 32 mCi [1.2 GBq]) was evaluated in 30 patients with mild thrombocytopenia (100-149 × 109 platelets/L) who had advanced, relapsed or refractory, low-grade, follicular, or transformed B-cell NHL. The ibritumomab tiuxetan regimen included an infusion of rituximab (250 mg/m2) and injection of 111In ibritumomab tiuxetan (5 mCi [185 MBq]) for dosimetry evaluation, followed 1 week later with rituximab (250 mg/m2) and90Y ibritumomab tiuxetan (0.3 mCi/kg [11 MBq/kg]). Patients (median age, 61 years; 90% stage III/IV at study entry; 83% follicular lymphoma; and 67% with bone marrow involvement) had a median of 2 prior therapy regimens (range, 1-9). Estimated radiation-absorbed doses were well below the study-defined maximum allowable for all 30 patients. With the use of the International Workshop criteria for NHL response assessment, the overall response rate was 83% (37% complete response, 6.7% complete response unconfirmed, and 40% partial response). Kaplan-Meier estimated median time to progression (TTP) was 9.4 months (range, 1.7-24.6). In responders, Kaplan-Meier estimated median TTP was 12.6 months (range, 4.9-24.6), with 35% of data censored. Toxicity was primarily hematologic, transient, and reversible. The incidence of grade 4 neutropenia, thrombocytopenia, and anemia was 33%, 13%, and 3%, respectively. Reduced-dose ibritumomab tiuxetan is safe and well tolerated and has significant clinical activity in this patient population.

PURPOSE: Radioimmunotherapy combines biologic and radiolytic mechanisms to target and destroy tumor cells, thus offering a needed therapeutic alternative for refractory non-Hodgkin’s lymphoma (NHL) patients. This phase III randomized study compares the novel radioimmunotherapy yttrium-90 (90Y) ibritumomab tiuxetan with a control immunotherapy, rituximab, in 143 patients with relapsed or refractory low-grade, follicular, or transformed CD20+transformed NHL.PATIENTS AND METHODS: Patients received either a single intravenous (IV) dose of90Y ibritumomab tiuxetan 0.4 mCi/kg (n = 73) or rituximab 375 mg/m2IV weekly for four doses (n = 70). The radioimmunotherapy group was pretreated with two rituximab doses (250 mg/m2) to improve biodistribution and one dose of indium-111 ibritumomab tiuxetan for imaging and dosimetry. The primary end point, overall response rate (ORR), was assessed by an independent, blinded, lymphoma expert panel.RESULTS: ORR was 80% for the90Y ibritumomab tiuxetan group versus 56% for the rituximab group (P = .002). Complete response (CR) rates were 30% and 16% in the90Y ibritumomab tiuxetan and rituximab groups, respectively (P = .04). An additional 4% achieved an unconfirmed CR in each group. Kaplan-Meier estimated median duration of response was 14.2 months in the90Y ibritumomab tiuxetan group versus 12.1 months in the control group (P = .6), and time to progression was 11.2 versus 10.1 months (P = .173) in all patients. Durable responses of ≥ 6 months were 64% versus 47% (P = .030). Reversible myelosuppression was the primary toxicity noted with90Y ibritumomab tiuxetan.CONCLUSION: Radioimmunotherapy with90Y ibritumomab tiuxetan is well tolerated and produces statistically and clinically significant higher ORR and CR compared with rituximab alone.