Donk, N. W. van de

Background:IBER is a novel cereblon E3 ligase modulator (CELMoD) with enhanced tumoricidal and immunostimulatory activities. Preclinically, IBER overcomes immunomodulatory drug (IMiD) resistance and has synergy with daratumumab (DARA), bortezomib (BORT), and dexamethasone (DEX).Aims:This phase 1b/2a multicenter, open‐label, dose‐escalation study (NCT02773030) was conducted to evaluate the maximum tolerated dose (MTD), recommended phase 2 dose (RP2D), safety and preliminary efficacy of IBER in combination with DEX, in patients with relapsed/refractory multiple myeloma (RRMM).Methods:Eligible patients had RRMM and must have received ≥2 prior regimens including lenalidomide (LEN) and/or pomalidomide (POM), and a proteasome inhibitor (PI). All patients had progressed on or within 60 days of last MM therapy. Escalating doses of IBER were given on days 1–21, in combination with DEX 40 mg (20 mg in patients aged >75 years) on days 1, 8, 15, and 22, of each 28‐day cycle. Dose escalation was reviewed by a dose escalation committee.Results:As of January 2019, 58 patients had received IBER + DEX. Median age was 64.5 years (range 33–79), and median number of prior regimens was 5 (2–12). Prior therapies included autologous stem cell transplantation (79%), LEN (100%), POM (69%), PIs (100%), and DARA (66%). IBER dose ranged from 0.3 to 1.2 mg; MTD/RP2D was not reached. Median duration of therapy was 12+ weeks (range 4–109). Grade 3–4 adverse events (AEs) were reported in 41 (72%) patients and were not related to dose. Grade 3–4 neutropenia, thrombocytopenia, neuropathy, and fatigue occurred in 26%, 11%, 2%, and 0% patients, respectively. Three patients discontinued treatment due to AEs. Clinical activity occurred early and was observed across all dose levels (Table 1); 20 of 51 patients remain on treatment (2–27+ cycles).Summary/Conclusion:IBER + DEX showed favorable efficacy and safety in heavily pretreated patients with RRMM who failed multiple prior therapies. This study is ongoing, including combinations of IBER with DARA or BORT.image

Background:Iberdomide (IBER) is a novel cereblon (CRBN) E3 ligase modulatory compound (CELMoD) that is being investigated as monotherapy, in combination with dexamethasone (DEX), and in combination with DEX and daratumumab or bortezomib in a phase 1b/2a dose‐escalation study in relapsed/refractory multiple myeloma (RRMM). IBER modulates CRBN, which induces ubiquitination of Aiolos, Ikaros and ZFP91, increases their proteasome‐dependent degradation, and thereby inhibits myeloma cell growth. IBER binds more potently to CRBN and is more efficient at degrading Aiolos and Ikaros than the immunomodulatory agents (IMiDs) lenalidomide (LEN) and pomalidomide (POM) and it can overcome IMiD drug resistance in pre‐clinical models.Aims:To determine if IBER is pharmacodynamically (PD) active in multiple myeloma patients refractory to POM and/or LEN, and to establish pharmacokinetic (PK)/PD and PD/dose relationships.Methods:As of Jan 11, 2019, 83 patients received IBER as monotherapy or in combination with DEX; 61 (74%) were LEN refractory and 47 (57%) were POM refractory. Longitudinal immunohistochemistry (IHC) data on CRBN, Aiolos, Ikaros and ZFP91 expression was obtained from bone marrow samples from 14 patients dosed with 0.3–0.9 mg IBER daily ± DEX. PD analysis of immune activity by TruCulture® (n = 45) and by peripheral blood flow cytometry (n = 60) was completed on a subset of patients dosed up to 1.0 mg IBER ± DEX. A population PK approach was used to estimate exposure (area under the concentration curve over the 24 hr dosing interval [AUCτ]) on 59 patients dosed up to 1.0 mg IBER ± DEX.Results:IBER AUCτ increased in a dose‐proportional manner in RRMM patients over the dose range 0.3–1.0 mg (22.4–65.31 ng∗hr/mL, respectively). In patient biopsies analyzed to date, CRBN expression was observed in all tumors by IHC at baseline and did not significantly change while on‐treatment. Furthermore, no significant decrease in baseline CRBN expression was observed in patients refractory to POM. In MM cells, significant decreases in Aiolos (median 37% decrease, P < 0.001), Ikaros (median 12% decrease, P = 0.006), and ZFP91 (median 47% decrease, P < 0.001) protein expression were observed on‐treatment across all dose levels; these decreases were unrelated to levels of CRBN expression at screening or prior LEN or POM refractoriness. In TruCulture® samples, dose‐dependent increases were observed in IL‐2 and IFN‐γ, with median increases of 78% and 66%, respectively, 5 hours post 0.9 mg dose of IBER. A dose‐ and exposure‐dependent decrease in B‐cells was detected (median 74% decrease at cycle 2 day 15, IBER 0.9 mg). These observations are consistent with the proposed IBER mechanism of action. Immunoprofiling showed significant increases in total and proliferating NK cells in RRMM patients treated with IBER, and a dose‐dependent increase in proliferating, activated, and effector memory T‐cells. These trends were consistent in RRMM patients treated with IBER monotherapy and in combination with DEX.Summary/Conclusion:These translational analyses from IBER treated RRMM patients indicate it is pharmacodynamically active at the lowest dose (0.3 mg) and exhibits dose‐ and exposure‐dependent immunostimulatory activity, supporting further dose‐escalation beyond 1.0 mg, which is currently ongoing. These results also suggest that prior refractoriness to LEN or POM is not associated with significant loss of CRBN or IBER PD activity, supporting continued investigation of IBER in RRMM patients refractory to IMiD drugs.