Abstract: Production of high specific activity 186g Re is of interest for development of theranostic radiopharmaceuticals. Previous studies have shown that high specific activity 186g Re can be obtained by cyclotron irradiation of enriched 186 W via the 186 W(d,2n) 186g Re reaction, but most irradiations were conducted at low beam currents and for short durations. In this investigation, enriched 186 W metal targets were irradiated at high incident deuteron beam currents to demonstrate production rates and contaminants produced when using thick targets. Full-stopping thick targets, as determined using SRIM, were prepared by uniaxial pressing of powdered natural abundance W metal or 96.86% enriched 186 W metal encased between two layers of graphite flakes for target material stabilization. An assessment of structural integrity was made on each target preparation. To assess the performance of graphite-encased thick 186 W metal targets, along with the impact of encasing on the separation chemistry, targets were first irradiated using a 22 MeV deuteron beam for 10 min at 10, 20, and 27 μA, with an estimated nominal deuteron energy of 18.7 MeV on the 186 W target material (after energy degradation correction from top graphite layer). Gamma-ray spectrometry was performed post EOB on all targets to assess production yields and radionuclidic byproducts. The investigation also evaluated a method to recover and recycle enriched target material from a column isolation procedure. Material composition analyses of target materials, pass-through/wash solutions and recycling process isolates were conducted with SEM, FTIR, XRD, EDS and ICP-MS spectrometry. To demonstrate scaled-up production, a graphite-encased 186 W target made from recycled 186 W was irradiated for ~2 h with 18.7 MeV deuterons at a beam current of 27 μA to provide 0.90 GBq (24.3 mCi) of 186g Re, decay-corrected to the end of bombardment. ICP-MS analysis of the isolated 186g Re solution provided data that indicated the specific activity of 186g Re in this scaled-up production run was 2.6±0.5 GBq/μg (70±10 Ci/mg).

Abstract: Animals select habitats based on food, water, space, and cover. Each of those components are essential to the ability of an individual to survive and reproduce in a particular habitat. Selection of resources is linked to reproductive fitness and individuals likely vary in how they select resources relative to their reproductive state: during pregnancy, while provisioning young when nutritional needs of the mother are high, but offspring are vulnerable to predation, or if they lose young to mortality. We investigated the effects of reproductive state on selection of resources by maternal female desert bighorn sheep ( Ovis canadensis nelsoni ) by comparing selection during the last trimester of gestation, following parturition when females were provisioning dependent young, and if the female lost an offspring. We captured, and recaptured each year, 32 female bighorn sheep at Lone Mountain, Nevada, during 2016–2018. Captured females were fit with GPS collars and those that were pregnant received vaginal implant transmitters. We used a Bayesian approach to estimate differences in selection between females provisioning and not provisioning offspring, as well as the length of time it took for females with offspring to return levels of selection similar to that observed prior to parturition. Females that were not provisioning offspring selected areas with higher risk of predation, but greater nutritional resources than those that were provisioning dependent young. When females were provisioning young immediately following parturition, females selected areas that were safe from predators, but had lower nutritional resources. Females displayed varying rates of return to selection strategies associated with access to nutritional resources as young grew and became more agile and less dependent on mothers. We observed clear and substantial shifts in selection of resources associated with reproductive state, and females exhibited tradeoffs in favor of areas that were safer from predators when provisioning dependent young despite loss of nutritional resources to support lactation. As young grew and became less vulnerable to predators, females returned to levels of selection that provided access to nutritional resources to restore somatic reserves lost during lactation.

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 303 Background: Carfilzomib (CFZ) is a novel proteasome inhibitor that binds its target selectively and irreversibly, resulting in greater and more sustained proteasomal inhibition compared to BTZ (Demo et al, Cancer Res 2007). CFZ overcomes BTZ-resistance in vitro (Kuhn et al, Blood 2007) and in a previous Phase 2 study (PX-171-003), single-agent CFZ achieved durable responses and maintained disease control [e.g. ≥ Stable Disease (SD)] in patients with progressive multiple myeloma (MM) despite treatment with essentially all available agents. PX-171-004 is an ongoing Phase 2 study of CFZ monotherapy in MM patients with relapsed or refractory disease following 1–3 prior therapies. Here we report updated data for the BTZ-treated cohort. Methods: Patients with relapsed or refractory (defined as 〈 25% response or disease progression during therapy) MM were enrolled and stratified based on prior BTZ exposure (e.g. BTZ-naïve and BTZ-treated). For the BTZ-treated cohort, tolerability and response to prior BTZ [≥ Minor Response (MR)] was not required. CFZ 20 mg/m2 IV was administered on Days 1, 2, 8, 9, 15 and 16 every 28 days, for up to 12 cycles. The primary endpoint was Overall Response Rate (ORR) [≥ Partial Response (PR)] by IMWG criteria. Secondary endpoints included Clinical Benefit Response (CBR = ORR + MR) and safety. Results: Thirty-five BTZ-treated patients were enrolled. Six (17%) patients had previously received BTZ exclusively as a single agent, 15 (43%) received BTZ as part of a chemotherapy combination and 10 (29%) received BTZ as part of a stem cell transplant (SCT) regimen. An additional 4 (11%) received BTZ in a chemotherapy combination as well as part of a separate transplant regimen. Other prior therapies included alkylators (89%), SCT (81%), thalidomide (69%), lenalidomide (37%), and anthracyclines (31%). Six (17%) patients had disease refractory to BTZ and 9 (26%) additional patients had discontinued BTZ due to toxicities. At baseline, 19 (54 %) patients had an ECOG score ≥ 1, 17 (49%) patients had neuropathy of Grade ≥ 1, 9 (26%) patients had impaired renal function (CrCl 〈 60 mL/min) and 9 (26%) had diabetes. The median time since diagnosis was 3.6 years (range 1.2–13.2). To date, the mean number of CFZ doses administered was 29.3 (∼5 four-week cycles; range 4–72 doses, 0.7–12 cycles). Thirty-three patients who initiated therapy were evaluable for response per protocol. The ORR was 18% (6/33), including 1 CR and 5 PRs. An additional 4 (12%) patients had MR (CBR= 30%) and 13 (39%) had SD for ≥ 6 weeks. For evaluable patients who were either refractory or intolerant to their prior BTZ therapy, responses to CFZ included 1 PR and 1 MR and 8 SDs. The most common adverse events (AEs) (≥ 30% patients) were primarily Grades 1/2 and included fatigue (57%), nausea (54%), vomiting (37%), dyspnea (34%), diarrhea (34%), anemia (31%), increased creatinine (31%) and upper respiratory tract infection (31%). Grade 3/4 AEs occurring in ≥ 10% of patients were anemia (14.3%) and neutropenia (11.4%). There were no reports of febrile neutropenia. Dose modifications were rarely required. Peripheral neuropathy (PN) was uncommon (4 patients, 11%); only 1 patient had a Grade 3 event that lasted 〈 36 hours and did not result in missed doses or dose modification. None of the 9 patients with baseline renal impairment were discontinued for renal AEs. To date, 6 (17%) patients have completed the full 12-cycle protocol at the initial dose and schedule, 6 (17%) remain on study and 1 patient has received 〉 19 cycles on a recently initiated extended treatment protocol. Conclusions: In a BTZ-exposed population that includes BTZ treatment failures and significant comorbidities (e.g. diabetes, renal insufficiency, etc), the 18% ORR (CBR 30%) is notable for this steroid- and anthracycline-sparing regimen. Single-agent CFZ is well tolerated, even in patients with renal insufficiency, and both myelosuppression and PN are uncommon. These data support the continuing evaluation of CFZ as a safe and effective treatment option in MM. Disclosures: Siegel: Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Millennium: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Wang:Proteolix, Inc.: Research Funding. Stewart:Genzyme, Celgene, Millenium, Proteolix: Honoraria; Takeda, Millenium: Research Funding; Takeda-Millenium, Celgene, Novartis, Amgen: Consultancy. Kukreti:Celgene: Honoraria. Jakubowiak:Millennium Pharmaceuticals, Inc.: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Celgene: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Centocor Ortho Biotech: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Exelixis: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Bristol-Myers-Squibb: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. 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. Belch:Ortho Biotech: Honoraria, Research Funding. Bahlis:Celgene: Honoraria, Speakers Bureau; Ortho Biotech: Honoraria, Speakers Bureau. Le:Proteolix, Inc.: Employment. Kunkel:Proteolix: Consultancy, Employment. Bennett:Proteolix: Employment. Kauffman:Proteolix, Inc.: Employment. Vij:Proteolix, Inc.: Consultancy, Research Funding.