Zonder, Jeffrey A.

Abstract Abstract 1845 Poster Board I-871 Background: Proteasome inhibition is an effective strategy for the treatment of multiple myeloma. In patients, proteasome inhibition has primarily been measured in peripheral blood samples (whole blood or mononuclear cells). However, it is unknown whether myeloma cells in the bone marrow (BM) are equally sensitive to proteasome inhibitors such as bortezomib (BTZ) and carfilzomib (CFZ). Aim: To measure proteasome inhibition in purified tumor cells from BM samples taken from patients enrolled in two ongoing Phase 2 trials of single agent CFZ in relapsed or refractory myeloma: PX-171-003 (003) and PX-171-004 (004). Methods: CFZ was administered as an IV bolus of 20 mg/m2 on Days 1, 2, 8, 9, 15 and 16 of a 28-day cycle on both trials. Bone marrow samples, from an optional sub-study of both trials, were taken during screening and Day 2 (post-treatment) and sorted into CD138+ and CD138− cells. Proteasome activity was measured by an enzymatic assay using a fluorogenic substrate (LLVY-AMC) for the chymotrypsin-like (CT-L) activity and an active site ELISA (ProCISE) to quantitate levels of the CT-L subunits of the constitutive proteasome (Beta5) and immunoproteasome (LMP7) and the immunoproteasome subunit MECL1. Results: Whole blood samples from patients treated with CFZ showed inhibition of CT-L activity of ∼80+, similar to values obtained in Phase 1 studies. A total of 10 CD138+ screening samples, 6 from 004 and 4 from 003, and 9 post-dose samples, 5 from 004 and 4 from 003, were analyzed for proteasome levels and activity. In addition, 15 CD138−screening samples, 7 from 004 and 8 from 003, and 9 post-dose samples, 5 from 004 and 4 from 003, were analyzed. When compared to the average base-line activity, CFZ treatment resulted in 88% CT-L inhibition in CD-138+tumor cells from 004 patients (P = 0.0212 by unpaired t-test) and 59% CT-L inhibition in CD-138+ tumor cells from 003 patients (P = 0.25). Baseline CT-L activity in CD138+ tumor cells was 3-fold higher in 004 than 003, which includes a more heavily pre-treated patient population with greater prior exposure to BTZ. Higher specific enzymatic activity was due to increased levels of both constitutive and immunoproteasomes in tumor cells, where immunoproteasomes account for >75% of total cellular proteasomes. No differences between trials were seen in baseline CT-L activity from non-tumor (CD138−) cells. Inhibition in CD138− cells was 84% (P = 0.0380 and 42% (P = 0.38) in 004 and 003, respectively. Using ProCISE, we measured inhibition of LMP7 (66%), beta5 (48%) and MECL1 (64%) in CD138+ tumor cells from 004 patients. Three patients from 004 and one from 003 had both a screening and post-dose tumor cell samples available for analysis. Inhibition of CT-L activity was >80% in two of the 3 patients on 004; the third patient showed no proteasome inhibition by ProCISE and was unavailable for analysis by CT-L. CT-L activity in the CD138+ tumor cells in the 003 patient was not inhibited, however, inhibition was seen in non-tumor cells. Conclusions: CFZ inhibits the proteasome activity of myeloma cells in the bone marrow of relapsed and refractory myeloma patients. The levels of inhibition were similar to those measured in whole blood samples, supporting the use of the blood-based assay as a surrogate marker for proteasome inhibition in tumor cells. CFZ treatment resulted in inhibition of both CT-L subunits as well as additional subunits of the immunoproteasome in tumor cells. Reduced baseline activity in the more heavily pretreated 003 patients may reflect reduced tumor-dependency on the proteasome and may be related to prior treatment with BTZ in these patients. More samples are needed in order to make correlations between levels of proteasome inhibition in bone marrow tumor cells and prior therapies or response. These observations support further evaluation of proteasome activity and the effects of this promising new agent in primary tumors cells from myeloma patients. Disclosures: Trudel: Celgene: Honoraria, Speakers Bureau; Ortho Biotech: Honoraria. Lee:Proteolix, Inc.: Employment. Kirk:Proteolix, Inc.: Employment. Lonial:Celgene: Consultancy; Millennium: Consultancy, Research Funding; BMS: Consultancy; Novartis: Consultancy; Gloucester: Research Funding. Wang:Proteolix, Inc.: Research Funding. Kukreti:Celgene: Honoraria. Stewart:Genzyme, Celgene, Millenium, Proteolix: Honoraria; Takeda, Millenium: Research Funding; Takeda-Millenium, Celgene, Novartis, Amgen: Consultancy. Jagannath:Millennium: Honoraria, Membership on an entity's Board of Directors or advisory committees; Merck: Honoraria, Membership on an entity's Board of Directors or advisory committees; Celgene: Membership on an entity's Board of Directors or advisory committees. McDonagh:Proteolix: Research Funding. Zonder:Celgene: Speakers Bureau; Pfizer: Consultancy; Seattle Genetics, Inc.: Research Funding; Amgen: Consultancy; Millennium: Research Funding. Bennett:Proteolix: Employment.

Abstract Abstract 731 Background: Treatment with bortezomib achieves high hematologic response rates and rapid and durable responses in AL patients (pts), providing the rationale for proteasome inhibition in this population. MLN9708 is an investigational, oral, potent, reversible, and specific 20S proteasome inhibitor (PI). In preclinical studies, MLN9708 has shown improved antitumor activity compared to bortezomib in a range of xenograft models. This phase 1 study (NCT01318902) assessed weekly doses of oral MLN9708 in pts with relapsed or refractory AL. Methods: Pts aged ≥18 years with relapsed or refractory AL after ≥1 prior therapy, cardiac biomarker stage I/II disease, and measurable major organ (heart/kidney) involvement, received increasing doses of oral MLN9708 (standard 3+3 dose escalation fixed doses of 4.0 and 5.5 mg), on days 1, 8, and 15 of 28-day cycles for up to 12 cycles. Pts with no major hematologic response (<PR) after 3 cycles received dexamethasone (dex; 40 mg, days 1–4). Two expansion cohorts of PI-naïve and PI-exposed pts were enrolled at the MTD. The primary objectives were to determine the safety, tolerability, and MTD. Secondary objectives included analysis of plasma pharmacokinetic (PK) and whole blood pharmacodynamic effects of MLN9708, and assessment of overall hematologic response rate, time to and duration of hematologic and organ response. Adverse events (AEs) were graded using NCI-CTCAE version 4.03. Blood samples were collected at multiple timepoints pre- and post-MLN9708 dosing for PK analysis during cycle 1. Hematologic response and amyloid-related organ assessments were performed according to standardized criteria. Results: At data cut-off (June 29, 2012) 16 pts had been enrolled and received ≥1 MLN9708 dose (safety population). The median age was 66.5 years (range 54–78) and 7 were male. Median number of prior therapies was 3 (range 1–7); 10 received prior transplant, 7 received prior bortezomib. Major organ involvement, defined by standard criteria, included heart, kidney, or both in 7/5/4 pts, respectively, with a median of 2 (range 1–5) involved organ systems, and Mayo cardiac biomarker risk stage was I, II, III in 6, 9, 1 pts. Five pts were treated in the 5.5 mg cohort and 11 pts were treated in the 4.0 mg (n=6 dose escalation; n=5 dose expansion) cohorts. Of the 11 pts treated at 4.0 mg, 4 were PI-naïve, 7 were PI-exposed. Pts received a median of 3 cycles (range 1–12); 5 pts received ≥5 cycles, and 8 pts remain on treatment. Dex was added in 4 pts (2 in each MLN9708 dose level). There were no on-study deaths. Pts discontinued due to disease progression (n=5), AE, withdrawal by pt, or unsatisfactory response (each n=1); 2 pts completed planned 1 year of therapy. One pt in the 4.0 mg cohort experienced a DLT of grade 3 thrombocytopenia. Two pts in the 5.5 mg dose cohort experienced DLTs: grade 3 diarrhea in 1 pt, and renal failure, respiratory failure (both grade 2), and cardiac arrest (grade 4) in another pt. The MTD was determined as 4.0 mg. AEs were reported in 14 pts. The most common drug-related AEs included nausea (n=5), diarrhea and thrombocytopenia (each n=4), abdominal pain and fatigue (each n=3). Grade ≥3 AEs (any cause) reported in >1 pt were thrombocytopenia (n=4), dyspnea (n=3), maculo-papular rash, dehydration, and abdominal pain (each n=2); all were grade 3. Preliminary response data are shown in the table. At data cut-off, one responder had progressed, and the median duration of hematologic response was 7.4 months (range 1.3–11.5+); 2 pts had cardiac organ response. Preliminary PK data showed that MLN9708 was rapidly absorbed, with a median Tmax of 1 hr (range 0.5–6). MLN9708 day 15 plasma Cmax was 73.6 ± 40.2 ng/mL (mean ± SD) and AUC0–168was 1250 ±530 ng*hr/mL (n=8 at 4.0 mg dose cohort). MLN9708 PK parameter values in this study appear similar to other MLN9708 studies in myeloma pts. Conclusions: These data suggest weekly oral administration of MLN9708 is feasible in pts with relapsed or refractory AL. The MLN9708 MTD was determined as 4.0 mg. Assessment is ongoing, with preliminary evidence of hematologic responses noted. A phase 3 study of MLN9708 plus dex versus physician's choice of treatment is planned (NCT01659658). Disclosures: Merlini: Millennium Pharmaceuticals, Inc.: Consultancy. Off Label Use: Use of the investigational agent MLN9708, an oral proteasome inhibitor, in the treatment of relapsed or refractory light-chain amyloidosis. Sanchorawala:Celgene: Research Funding; Millennium Pharmaceuticals, Inc.: Research Funding; Onyx: Research Funding. Zonder:Celgene: Research Funding; Millennium Pharmaceuticals, Inc: Consultancy, Research Funding. Kukreti:Roche: Consultancy, Honoraria; Celgene: Honoraria; Janssen: Honoraria. Schonland:Celgene: Honoraria, Research Funding; Janssen: Honoraria. Dispenzieri:Janssen Research & Development: Research Funding; Millennium Pharmaceuticals, Inc.: Research Funding; Celgene: Research Funding. Cohen:Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees; Bristol-Meyers Squibb: Honoraria, Membership on an entity's Board of Directors or advisory committees; Onyx: Honoraria, Membership on an entity's Board of Directors or advisory committees. Berg:Millennium Pharmaceuticals, Inc.: Employment. Liu:Millennium Pharmaceuticals, Inc.: Employment. Di Bacco:Millennium Pharmaceuticals, Inc.: Employment. Gupta:Millennium Pharmaceuticals, Inc.: Employment. Hui:Millennium Pharmaceuticals, Inc.: Employment. Comenzo:Millennium Pharmaceuticals, Inc.: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding.

Abstract Abstract 76 Background: We measured proliferation in MM cells transfected with 13,984 small interfering RNAs in the absence/presence of increasing concentrations of bortezomib (BTZ) and identified 37 non lethal genes as reproducible BTZ sensitizers. The strongest hit was CDK5 a gene expressed at high levels in MM and neural tissues with relatively low expression in other organs suggesting a large therapeutic window. The small molecule CDK5 inhibitor Dinaciclib is a novel, potent, small molecule inhibitor of cyclin dependent kinases (CDK). It selectively inhibits CDK1, CDK 2, CDK 5 and CDK9 with 50% inhibitory concentrations (IC50) in the low nanomolar concentration. Based on these data, we undertook the current trial to evaluate the maximally tolerated dose of Dinaciclib in this patient population as well as assess the efficacy of single agent Dinaciclib in relapsed MM. Patients and Methods: Patients with relapsed MM and measurable disease were enrolled on this phase 1/2 trial provided they had not more than 4 prior lines of therapy for MM, had adequate performance status and organ and hematological function. Patients receiving strong inhibitors/inducers of CYP3A4 were not allowed unless the drugs could be discontinued. The primary objectives were to (i) to determine the MTD of dinaciclib in subjects with relapsed MM (phase 1) and (ii) to evaluate the confirmed response rate with dinaciclib in patients with relapsed MM (phase 2). Dinaciclib was administered on day 1 of a 21-day cycle at doses of 30–50 mg/m2. Dose escalation was done using a 3+3 design and MTD was defined as one dose level below that resulted in >=2 DLTs among 6 patients. Results: Overall, twenty-nine patients were accrued to this study (19 phase I, 10 phase II) from July 2009 to December 2011. Two patients were replaced for study violations and are not included in analysis. The Phase II analysis included the 6 patients treated at the Phase I dose level 50mg/m2 as well as the first 9 patients accrued to the Phase II portion (15 evaluable patients). The median age of the 27 evaluable patients was 66 (range, 49–81); 52% were male. The median duration from diagnosis was 42 months (range, 7–207 months); median number of prior therapies was 4 (range, 1–5). Overall, 11 (41%) patients were considered high-risk by FISH and 56% were ISS stage III at study entry. Patients have received a median of 2 cycles (range: 1–12) and all patients have discontinued treatment for disease progression (18), alternative Treatment (2), adverse Event (4), or other reasons (3). One dose limiting toxicity was seen over all dose levels. One patient at 40 mg/m2 experienced grade 3 constipation possibly related to treatment. The dose level of 50 mg/m2 was determined to be the MTD for the Phase II portion. The overall confirmed response rate was 3 of 27 (11%); including two patients at 40 mg/m2 dose (1 VGPR, 1 PR) and one patient at 50 mg/m2 dose (1 VGPR) with a PR or better. In addition, two patients at 50 mg/mg2 dose have achieved an MR; translating to an overall response rate of 18.5% (5 of 27). Figure 1 shows a waterfall plot of the M protein responses among patients with a measurable M spike. Overall, 21 patients had disease progression and 14 patients have died. Median follow-up for patients still alive is 11.8 months (range: 6.5–19.3). Leukopenia and thrombocytopenia were the most common hematological AEs, and gastrointestinal symptoms, alopecia, and fatigue, were the most common non-hematological AEs seen in the study. Conclusions: The current study demonstrates potential single agent anti-myeloma activity of dinaciclib in a relapsed MM patient population with 2 patients achieving a deep response (VGPR) and many patients obtaining some degree of M protein stabilization or decrease. Ongoing studies are examining dinaciclib in combination with proteasome inhibitors, exploring both weekly and every three-week dosing schedules. Disclosures: Zonder: Millennium Pharmaceuticals, Inc: Consultancy, Research Funding; Celgene: Research Funding.

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.

SummarySelinexor, an oral Selective Inhibitor of Nuclear Export, targets Exportin 1 (XPO1, also termed CRM1). Non‐clinical studies support combining selinexor with proteasome inhibitors (PIs) and corticosteroids to overcome resistance in relapsed/refractory multiple myeloma (RRMM). We conducted a phase I dose‐escalation trial of twice‐weekly selinexor in combination with carfilzomib and dexamethasone (SKd) to determine maximum tolerated dose in patients with RRMM (N = 21), with an expansion cohort to assess activity in carfilzomib‐refractory disease and identify a recommended phase II dose (RP2D). During dose escalation, there was one dose‐limiting toxicity (cardiac failure). The RP2D of twice‐weekly SKd was selinexor 60 mg, carfilzomib 20/27 mg/m2 and dexamethasone 20 mg. The most common grade 3/4 treatment‐emergent adverse events included thrombocytopenia (71%), anaemia (33%), lymphopenia (33%), neutropenia (33%) and infections (24%). Rates of ≥minimal response, ≥partial response and very good partial response were 71%, 48% and 14%, respectively; similar response outcomes were observed for dual‐class refractory (PI and immunomodulatory drug)/quad‐exposed (carfilzomib, bortezomib, lenalidomide and pomalidomide) patients (n = 17), and patients refractory to carfilzomib in last line of therapy (n = 13). Median progression‐free survival was 3·7 months, and overall survival was 22·4 months in the overall population. SKd was tolerable and re‐established disease control in RRMM patients, including carfilzomib‐refractory patients.Registered at ClinicalTrials.gov (NCT02199665)