Final results of phase 1 evaluation of the safety and clinical activity of sapanisertib in combination with serabelisib and paclitaxel in patients with advanced ovarian, endometrial, or breast cancer.

2021 ◽  
Vol 39 (15_suppl) ◽  
pp. 5569-5569
Author(s):  
David Starks ◽  
Luis Alexander Rojas-Espaillat ◽  
Nandini Dey ◽  
Pradip De ◽  
Brian Leyland-Jones ◽  
...  

5569 Background: Evidence suggests that activation of the PI3K/AKT/mTOR pathway by paclitaxel may play a role in the development of taxane resistance. Conversely, PI3K inhibitors have been shown to sensitize tumors to the effects of paclitaxel. Therefore, the link between taxane resistance and activation of the PI3K/AKT/mTOR signaling pathway suggests inhibition of this pathway in combination with antimitotic drugs like paclitaxel may improve treatment outcomes in many malignancies. To further investigate this hypothesis we combined the TORC 1/2 inhibitor sapanisertib (TAK-228), the PI3Kα isoform inhibitor serabelisib (TAK-117), and paclitaxel in a phase I trial of heavily pretreated patients to determine the safety, efficacy, and RP2D. Methods: This is an open label, cohort study of sapanisertib (TAK-228) and serabelisib (TAK-117) given on days 2-4, 9-11, 16-18, and 23-25 with paclitaxel on days 1, 8, and 15 of a 28-day cycle. A traditional 3+3 dose escalation design with a maximum of 5 dosing cohorts was used. All 5 cohorts plus an expansion cohort are presented. Results: Enrollment has been completed and the overall results are summarized. Nineteen patients were enrolled; the majority were heavily pretreated with the average number of prior regimens exceeding 4. Based upon ITT, the ORR is 37%. The ORR is 47% in patients that completed at least 3 cycles. The clinical benefit rate is 73% and the PFS currently stands at approximately 11 months. Two patients with endometrioid endometrial adenocarcinoma achieved a complete response. All patients received comprehensive genomic profiling and 7 patients received prior mTOR inhibitor. Overall, the combination was well tolerated, except by patients in cohort 5. One DLT occurred in the last patient enrolled. The most common non-laboratory AEs were nausea (6%), fatigue (5%), and mucositis (5%). There were 45 (9%) grade 3 or 4 events, and the most common were decreased WBC and non-febrile neutropenia. Hyperglycemia was common in patients with a history of diabetes mellitus. Conclusions: Overall, the combination of sapanisertib, serabelisib, and paclitaxel was safe and efficacious throughout the first 4 cohorts. There were few serious adverse events, and most side effects were managed with routine supportive care interventions. Preliminary clinical results appear very promising, especially for patients with PI3K/AKT/mTOR pathway mutations. The positive effects of the combination were routinely seen in the lowest dosing cohorts and clinical benefit was even seen in patients that had previously failed everolimus or temsirolimus. All patients were either resistant or refractory to paclitaxel at time of enrollment, so further exploration of this combination to elucidate the mechanism of benefit is warranted. Clinical trial information: NCT03154294.

2020 ◽  
Vol 38 (15_suppl) ◽  
pp. 3604-3604
Author(s):  
Casey B. Williams ◽  
Kirstin Anne Williams ◽  
Amy K. Krie ◽  
Pradip De ◽  
Nandini Dey ◽  
...  

3604 Background: The link between taxane resistance and activation of PI3K/AKT/mTOR signaling suggests that by inhibiting this pathway in combination with anti-microtubule agents like paclitaxel may improve treatment outcomes in many malignancies. To investigate this further we combined the TORC 1/2 inhibitor sapanisertib (TAK-228), the PI3Kα isoform inhibitor serabelisib (TAK-117), and paclitaxel in a phase I trial to determine the safety, efficacy, and RP2D. Methods: Open label, cohort study using a traditional 3+3 dose escalation design with a maximum of 5 dosing cohorts. A dose expansion of cohort 4, the recommended RP2D, is planned for February 2020. Results: Enrollment to the DLT evaluation has been completed and the clinical results are summarized in Table. Sixteen patients have been enrolled; a majority were heavily pretreated and resistant to paclitaxel. Overall, the combination was safe and tolerable. One DLT occurred due to renal dysfunction in cohort 5. 360 adverse events have been reported, but only 28 (8%) grade 3 or 4 events. The most common events were leukopenia and non-febrile neutropenia. Two patients required dose reductions as a result of pneumonitis. The ORR is currently 46% in 13 evaluable patients. CBR is 69% and PFS is currently at 10 months. Two patients achieved a CR and three patients remain on treatment. Conclusions: The combination proved to be well tolerated in the doses and schedules used in cohorts 1-4 and exhibited very promising clinical activity in heavily pretreated patients. This regimen could prove to be a highly effective treatment option and a phase 2 study is warranted at the RP2D. Clinical trial information: NCT03154294 . [Table: see text]


2021 ◽  
Vol 39 (15_suppl) ◽  
pp. 11534-11534
Author(s):  
Cesar Serrano ◽  
Claudia Valverde ◽  
Josefina Cruz Jurado ◽  
Javier Martinez-Trufero ◽  
Xavier Guri ◽  
...  

11534 Background: KIT or PDGFRA oncogenic activation drives GIST progression throughout the disease course. Accordingly, currently approved agents in metastatic GIST focus on the therapeutic suppression of these receptors. However, the clinical benefit after imatinib (IM) progression is still modest, suggesting the co-operation of KIT/PDGFRA-independent mechanisms in GIST cell survival. Selinexor is an oral, selective inhibitor of XPO1-mediated nuclear export, and preclinical studies evidenced antitumoral activity in GIST as single agent and in combination with IM in both IM-sensitive and IM-resistant models. Methods: The phase Ib portion studied IM 400 mg daily plus weekly selinexor in patients (pts) with IM-resistant, advanced GIST. Prior intolerance to IM was not allowed. A standard 3+3 dosing schema was utilized to determine the recommended phase II dose (RP2D) of this combination. Investigator-assessed response was evaluated every 8 weeks using RECIST 1.1. Results: At data cutoff of Sep 25, 2020, 12 pts were enrolled and received treatment with IM 400 mg and selinexor once weekly at dose levels (DL) 1 (60 mg), DL2 (80 mg) and DL3 (100 mg). Median age 57 (range 46-77), 42% female, median prior therapies 4 (range 2-7). Although only 1/6 pts developed a dose limiting toxicity (DLT) at DL3, the RP2D was defined at DL2 (IM 400 mg daily and selinexor 80 mg once weekly) based on activity data in the DL2 and the need for dose reductions in 5/6 pts at DL3 after the DLT window. All pts were evaluable for toxicity and response. One DLT occurred at DL3 (G3 nausea). Non-DLT G3/4 toxicities were anemia (1/12 pts), neutropenia (1/12 pts), vomiting (1/12 pts) and fatigue (2/12 pts). Common G1/2 toxicities were nausea (11/12 pts), vomiting (10/12 pts), neutropenia (5/12 pts) and anemia, fatigue, diarrhea, and periorbital edema (4/12 pts each). No unexpected toxicities were observed. Overall response rate in the 12 pts evaluable for response was 67% (95% CI 0.349-0.901), with 2 pts achieving PR (17%) and 6 pts SD (50%) as the best response. Clinical benefit rate (CBR = CR, PR, SD) ≥ 16 weeks was 42% (95% CI 0.157-0.723). Median progression free survival was 3.5 months (95% CI 1.7-7.3). Four pts remain on trial at data cutoff. Conclusions: IM and selinexor combination is well-tolerated and has clinical activity in heavily pretreated GIST pts. The trial is currently exploring selinexor as single agent in the IM-resistant GIST population. Clinical trial information: NCT04138381.


Author(s):  
Wenhui Zhang ◽  
Astrid Scalori ◽  
Franklin Fuh ◽  
Jacqueline McBride ◽  
Gaohong She ◽  
...  

Abstract Background Etrolizumab, a humanized anti-β7 antibody, has not been studied in children. Here, we evaluate the pharmacokinetics, pharmacodynamics, and safety of etrolizumab in children with inflammatory bowel disease. Methods Patients age 4 to 17 years with moderately to severely active ulcerative colitis or Crohn’s disease were randomized 1:1 to receive 1.5mg/kg of etrolizumab subcutaneously every 4 weeks (q4w) or 3.0mg/kg every 8 weeks (q8w) for 16 weeks in this open-label phase 1 trial. Pharmacokinetics, pharmacodynamics, safety, and efficacy were assessed. Results Of the 24 patients treated, 21 completed the study. In the groups of 1.5mg/kg q4w and 3.0mg/kg q8w, respectively, mean (SD) maximum concentration (Cmax) was 9.8 (4.86) µg/mL and 18.1 (6.25) µg/mL; and mean (SD) area under the curve within a dosing interval (AUCtau) was 167 (86.9) and 521 (306) μg·day/mL after the last dose. The Cmax increased dose proportionally. The AUC over an 8-week period was slightly higher in the 3.0mg/kg q8w dose group. Median half-life was similar for both dosing regimens. Median numbers of free β7high gut-homing T and B cell subsets declined below 10% of baseline, confirming β7 target engagement and complete/near-complete receptor occupancy. Adverse events were consistent with the safety profile in adults. Approximately 60% of patients achieved a clinical response. Conclusions Etrolizumab showed a dose-proportional increase in Cmax and a slightly greater than dose-proportional increase in AUCtau. Both regimens achieved complete/near-complete β7 receptor occupancy, with a similar relationship to concentration as adults. Etrolizumab was well tolerated and demonstrated clinical activity in children.


2021 ◽  
Vol 39 (15_suppl) ◽  
pp. 5565-5565
Author(s):  
Shannon Neville Westin ◽  
Siqing Fu ◽  
Apostolia Maria Tsimberidou ◽  
Sarina Anne Anne Piha-Paul ◽  
Fechukwu Akhmedzhanov ◽  
...  

5565 Background: Selinexor is a first-in-class novel, oral potent selective inhibitor of nuclear export (SINE) which blocks Exportin-1 (XPO1) leading to nuclear accumulation and activation of tumor suppressor proteins and prevention of translation of proto-oncogenes. Weekly paclitaxel is a standard chemotherapy regimen used in various tumor types. Preclinical models show that selinexor with paclitaxel exerts antitumor activity against multiple solid tumors. Our objective was to determine the maximum tolerated dose (MTD) and recommended phase II dose (RP2D) of selinexor and weekly paclitaxel. Methods: This was an open label, single-center, multi-arm phase 1b study utilizing a “3 + 3” design and a “basket type” expansion. Selinexor (twice weekly orally) and weekly paclitaxel (80mg IV 2 week on, 1 week off) was employed as one of 13 parallel arms. Two dose levels (DL) of selinexor were explored: DL1 selinexor 60mg; DL2 selinexor 80mg. Patients (pts) with advanced or metastatic solid tumors were eligible if they had adequate bone marrow and organ function. There was no limit on prior lines of therapy. Efficacy was evaluated using RECIST 1.1. Progression free survival (PFS) was defined as time from treatment until disease progression or death. Results: Of 35 pts treated, all were evaluable for toxicity, and 31 (88%) were evaluable for response. Pt diagnoses included ovarian (n = 28), breast (n = 4), prostate (n = 2), and cervical (n = 1) cancer. Pts had a median of four prior therapies (range 1-10), and 47% had a prior taxane. All pts with ovarian cancer had platinum resistant/refractory disease; high grade serous histology was most common. There were no DLTs and DL1 was chosen as the RP2D given its long term tolerability. 97% of pts had at least one treatment-emergent adverse event (TEAE) and the most common TEAEs were anemia (74%), nausea (57%), fatigue (51%), leukopenia (51%), neutropenia (49%), thrombocytopenia (46%), and vomiting (31%). The most prevalent grade ≥ 3 TEAE were neutropenia (46%), anemia (31%), leukopenia (17%), and fatigue (9 %). Partial responses (PR) were noted in 4 pts (13%); 10 pts (32%) achieved stable disease for > 4 months for a clinical benefit rate (CBR) of 45%. 16 pts (47%) had prior exposure to a taxane, including 1 pt who achieved PR. Among 24 evaluable pts with ovarian cancer, response rate was 17%, CBR was 58%, and PFS was 6.83 months (95% CI 3.73, not reached (NR)). Median duration of clinical benefit in ovarian cancer was 7.57 months (95% CI: 4.43, NR). Conclusions: Oral selinexor in combination with weekly paclitaxel demonstrated promising clinical activity with manageable toxicity, and further evaluation with once weekly selinexor is warranted. This combination should be considered for further exploration in a randomized study, especially in ovarian malignancies. Clinical trial information: NCT02419495.


2021 ◽  
Vol 39 (3_suppl) ◽  
pp. TPS150-TPS150
Author(s):  
Michael Cecchini ◽  
Kartik Krishnan ◽  
Nick Giafis ◽  
Jennifer Scott ◽  
Cheng Seok Quah ◽  
...  

TPS150 Background: ATP release from dying cancer cells in response to platinum-based chemotherapy increases extracellular immunosuppressive adenosine, which binds and activates the A2a and A2b receptors on immune cells. Adenosine-mediated signaling impairs activation, proliferation, and cytotoxic activity of effector T cells, resulting in inhibition of antitumor activity. Concomitant adenosine receptor blockade may therefore enhance the therapeutic efficacy of chemo/immunotherapy regimens. Etrumadenant (AB928), the first clinical-stage, small-molecule, dual adenosine receptor antagonist, is highly potent, pharmacodynamically active, and has been well tolerated in dose escalation studies as monotherapy or combined with chemo/immunotherapy. Recently, results were reported for the ARC-3 phase 1/1b study of etrumadenant + modified 5-fluorouracil + oxaliplatin (mFOLFOX-6) in patients (pts) with mCRC. In this study, etrumadenant + mFOLFOX-6 was well tolerated without significant additive toxicity. Disease control was observed in patients with RAS/BRAF mutated mCRC, as well as 3L+ disease previously treated with FOLFOX and/or FOLFIRI (PR and/or SD >4 mo). Due to deep responses in 1L-3L+ pts, 6 pts had the opportunity to pursue surgery and radiotherapy with curative intent. The encouraging results from ARC-3 warrant further evaluation of etrumadenant-based combination therapy for mCRC. Methods: ARC-9 is a phase 1b/2, multicohort, open-label, randomized platform study designed to evaluate safety and clinical activity of etrumadenant (150 mg orally once daily [QD]) in combination with standard-of-care (SOC) regimens or novel therapeutics in pts with mCRC (Table). Cohort eligibility is based on prior anticancer treatment history. Pts enrolled in Cohorts A and B will be randomized (2:1) into the experimental vs SOC arms. Cohort C consists of a single arm to allow inclusion of novel agents as they become available with built in early stopping rules for futility. Pts who progress on the SOC arm of Cohort A can enroll in Cohort B; pts who progress on the SOC arm of Cohort B can crossover to the experimental arm. Primary endpoints across cohorts are shown in Table. Safety monitoring will occur throughout the trial, disease assessments will occur every 8 weeks, and correlative study pre- and on-treatment biopsies will be performed. [Table: see text]


2020 ◽  
Vol 9 (9) ◽  
pp. 2816
Author(s):  
Lara Sánchez-Bilbao ◽  
David Martínez-López ◽  
Marcelino Revenga ◽  
Ángel López-Vázquez ◽  
Elia Valls-Pascual ◽  
...  

Graves’ orbitopathy (GO) is the most common extrathyroidal manifestation of Graves’ disease (GD). Our aim was to assess the efficacy and safety of Tocilizumab (TCZ) in GO refractory to conventional therapy. This was an open-label multicenter study of glucocorticoid-resistant GO treated with TCZ. The main outcomes were the best-corrected visual acuity (BVCA), Clinical Activity Score (CAS) and intraocular pressure (IOP). These outcome variables were assessed at baseline, 1st, 3rd, 6th and 12th month after TCZ therapy onset. The severity of GO was assessed according to the European Group on Graves’ Orbitopathy (EUGOGO). We studied 48 (38 women and 10 men) patients (95 eyes); mean age ± standard deviation 51 ± 11.8 years. Before TCZ and besides oral glucocorticoids, they had received IV methylprednisolone (n = 43), or selenium (n = 11). GO disease was moderate (n =29) or severe (n = 19) and dysthyroid optic neuropathy (DON) (n = 7). TCZ was used in monotherapy (n = 45) or combined (n = 3) at a dose of 8 mg/kg IV every four weeks (n = 43) or 162 mg/s.c. every week (n = 5). TCZ yielded a significant improvement in all of the main outcomes at the 1st month that was maintained at one year. Comparing the baseline with data at 1 year all of the variables improved; BCVA (0.78 ± 0.25 vs. 0.9 ± 0.16; p = 0.0001), CAS (4.64 ± 1.5 vs. 1.05 ± 1.27; p = 0.0001) and intraocular pressure (IOP) (19.05 ± 4.1 vs. 16.73 ± 3.4 mmHg; p = 0.007). After a mean follow-up of 16.1 ± 2.1 months, low disease activity (CAS ≤ 3), was achieved in 88 eyes (92.6%) and TCZ was withdrawn in 29 cases due to low disease activity (n = 25) or inefficacy (n = 4). No serious adverse events were observed. In conclusion, TCZ is a useful and safe therapeutic option in refractory GO treatment.


Author(s):  
Timothy P Endy ◽  
Dongliang Wang ◽  
Mark E Polhemus ◽  
Richard G Jarman ◽  
Louis E Jasper ◽  
...  

Abstract Background Dengue human infection models (DHIM) have been used as a safe means to test the viability of prophylaxis and therapeutics. Methods A phase 1 study of 12 healthy adult volunteers using a challenge virus, DENV-1-LVHC strain 45AZ5, was performed. A dose escalating design was used to determine the safety and performance profile of the challenge virus. Subjects were evaluated extensively until 28 days and then out to 6 months. Results Twelve subjects received the challenge virus: 6 with 0.5 mL of 6.5 × 103 plaque-forming units (PFU)/mL (low-dose group) and 6 with 0.5 mL of 6.5 × 104 PFU/mL (mid-dose group). All except 1 in the low-dose group developed detectable viremia. For all subjects the mean incubation period was 5.9 days (range 5–9 days) and mean time of viremia was 6.8 days (range 3–9 days). Mean peak for all subjects was 1.6 × 107 genome equivalents (GE)/mL (range 4.6 × 103 to 5 × 107 GE/mL). There were no serious adverse events or long-term safety signals noted. Conclusions We conclude that DENV-1-LVHC was well-tolerated, resulted in an uncomplicated dengue illness, and may be a suitable DHIM for therapeutic and prophylactic product testing. Clinical Trials Registration NCT02372175.


Blood ◽  
2006 ◽  
Vol 108 (11) ◽  
pp. 1149-1149
Author(s):  
Bruce A. Wallin ◽  
Denise Ramjit ◽  
Michael Seiberling ◽  
David Zopf

Abstract NE-180 is a glycoPEGylated recombinant human erythropoietin that binds to and activates the erythropoietin (EPO) receptor. It has demonstrated in vitro activities comparable to EPO and an extended serum half-life in animal studies. This may allow less frequent dosing in patients being treated with chronic anemia. METHODS: A single center, open-label study of NE-180, administered as single escalating doses given by the SC or IV route, was conducted to assess the safety, tolerability, PK and PD. Subjects (male or female NHV) were planned to be assigned to one of 4 dose groups, 10 subjects per dose with 5 SC and 5 IV subjects per group: 0.5, 1.5, 3, or 4.5 mg/kg. Each dose group was planned to be initiated in an ascending, sequential fashion unless or until stopping rules were met. RESULTS: 25 NHV (16 females) were enrolled in the first two dose cohorts and have completed 56 day follow-up. The 1.5 mg/kg IV cohort met the protocol-specified Hb rate of rise stopping rule (change in Hb greater than 1 g/dL during any 14 day period). Injections were generally well tolerated with no discontinuations for adverse events or serious adverse events. Reticulocyte increases were dose proportional. Average reticulocyte count at baseline was 1.0±0.3%. The maximal increase occurred at day 7. The mean change from baseline for the 0.5 and 1.5 mg/kg SC group was: 0.9±0.4% and 2.2±0.9%, respectively. The mean change from baseline for the 0.5 and 1.5 mg/kg IV group was: 1.7±0.8% and 2.3±0.8%, respectively. PK data will be presented. CONCLUSIONS: Single doses up to 1.5 mg/kg of NE-180 administered to NHV were generally well tolerated and demonstrated potent dose-dependent erythropoietic activity.


Blood ◽  
2008 ◽  
Vol 112 (11) ◽  
pp. 864-864 ◽  
Author(s):  
Sundar Jagannath ◽  
Ravi Vij ◽  
A. Keith Stewart ◽  
George Somlo ◽  
Andrzej Jakubowiak ◽  
...  

Abstract Background: Carfilzomib (CFZ) is a novel proteasome inhibitor of the epoxyketone class that exhibits a high level of selectivity for the proteasome and has been shown in a phase 1 study to result in greater than 80% proteasome inhibition on a QDx2 consecutive day schedule. We piloted this agent in MM patients with relapsed and refractory disease, who had failed bortezomib (BTZ) and at least one immunomodulatory (IMiD) agent, e.g., thalidomide (THAL) and/or lenalidomide (LEN). Methods: PX-171-003 is an open-label, multicenter study enrolling pts with MM who have relapsed from at least 2 prior therapies and who are refractory; defined as progressing on or within 60 days of last therapy or<25% response to the last therapy. Pts received CFZ 20 mg/m2 IV Days 1, 2, 8, 9, 15 and 16 every 28 days, for up to 12 cycles. Dexamethasone 4 mg po was administered prior to each dose in Cycle 1. Responses were evaluated by the International Uniform Response Criteria for Multiple Myeloma. Clinical benefit response (CBR) was defined as complete response (CR) + partial/very good partial response (PR/VGPR) + minimal response (MR, as defined by EBMT criteria). Responses were adjudicated by an independent review committee. Results: 46 pts were enrolled, including 78% with progression on or within 60days of last therapy and 22% with no response to last therapy. 39 pts initiated treatment, completed at least one cycle of CFZ, had measurable M-protein, and were evaluable (eval) for response. The mean number of prior therapies (excluding transplant) was 6.4(range 1 to 18). 100% of pts received prior BTZ, 91% prior THAL, 89% prior LEN, and 83% prior stem cell transplantation (SCT). To date, pts received a median of 3 cycles(range 1–9) of CFZ; 22 started at least 4 cycles. The CBR was 26% (10/39 eval pts), including 5 pts achieving PR, 5 pts achieving MR, and 16 additional patients achieving stable disease (SD). Time to response was rapid, frequently occurring in the 1st cycle. CFZ was generally well tolerated; the most common adverse events (AEs) were fatigue(65%), nausea (37%), upper respiratory infection (37%), and diarrhea (33%). Worsening of hematologic parameters: anemia (65%); thrombocytopenia (46%) and neutropenia(20%) were predominantly Grades 1 and 2. Increased creatinine, both drug and non-drug related, was seen in 15/46 pts (33%), but treatment was discontinued in only 3 patients due to a renal adverse event. Acute renal failure was documented in 4 pts (9%), 2 (4%) of whom also had possible tumor lysis. 78% of pts had Grade 1 or 2 peripheral neuropathy (PN) at baseline. Exacerbation of PN was rare, and there were no study discontinuations or dose reductions due to PN. Conclusions: In the context of this heavily pre-treated MM population, single agent CFZ was able to induce CBR in 26% of MM patients, the majority of whom had failed BTZ, LEN, THAL, and SCT. CFZ was generally well-tolerated, and toxicities were manageable. Importantly, exacerbation of pre-existing PN was rare and did not result in dose reduction or discontinuation of therapy. These observations support further evaluation of CFZ as a promising new agent in MM. Enrollment is proceeding at an escalated dose (based on tolerability) in this trial. Additional studies of CFZ in patients who are less heavily pretreated and in combination with other chemotherapy agents are ongoing.


Blood ◽  
2010 ◽  
Vol 116 (21) ◽  
pp. 1959-1959 ◽  
Author(s):  
Jatin J Shah ◽  
Jeffrey A. Zonder ◽  
Adam Cohen ◽  
Donna Weber ◽  
Sheeba Thomas ◽  
...  

Abstract Abstract 1959 Background: Kinesin Spindle Protein (KSP) is required for cell cycle progression through mitosis. Inhibition of KSP induces mitotic arrest and cell death. ARRY-520 is a potent, selective KSP inhibitor. Cancers such as multiple myeloma (MM) which depend on the short-lived survival protein MCL-1 are highly sensitive to treatment with ARRY-520. ARRY-520 shows potent activity in preclinical MM models, providing a strong rationale for its clinical investigation in this disease. Methods: This Phase 1 study was designed to evaluate the safety and pharmacokinetics (PK) of ARRY-520 administered intravenously (IV) on Day 1 and Day 2 q 2 weeks without/with granulocyte-colony stimulating factor (G-CSF). Patients (pts) with relapsed/refractory (RR) MM with 2 prior lines of therapy (including both bortezomib and an immunomodulatory agent, unless ineligible for or refusing to receive this therapy) were eligible. Cohorts of at least 3 pts were enrolled in a classical 3 + 3 dose escalation design. Pts were treated for 2 cycles (4 weeks) to evaluate safety prior to dose escalation. Results: Twenty five pts have been treated to date, with a median age of 60 years (range 44–79) and a median of 5 prior regimens (range 2–16). All pts received prior bortezomib or carfilzomib, 21 pts received prior lenalidomide, 17 pts prior thalidomide, and 18 pts had a prior stem cell transplant. Pts received ARRY-520 without G-CSF at 1 mg/m2/day (n = 3), and at 1.25 mg/m2/day (n = 7, 6 evaluable). A dose-limiting toxicity (DLT) of Grade 4 neutropenia was observed at 1.25 mg/m2/day, and this was considered the maximum tolerated dose (MTD) without G-CSF. As neutropenia was the DLT, dose escalation with prophylactic G-CSF support was initiated, at doses of 1.5 mg/m2/day (n = 7, 6 evaluable), 2.0 mg/m2/day (n = 6) and 2.25 mg/m2/day (n = 2) with G-CSF. Both the 2.0 mg/m2/day and 2.25 mg/m2/day dose levels were determined to be non-tolerated, with DLTs of febrile neutropenia (FN) (2 pts at 2.0 mg/m2/day and both pts at 2.25 mg/m2/day) and Grade 3 mucositis (both pts at 2.25 mg/m2/day). One out of 6 evaluable pts at 1.5 mg/m2/day also developed a DLT of FN. In an attempt to optimize the Phase 2 dose, an intermediate dose level of 1.75 mg/m2/day with G-CSF is currently being evaluated. The most commonly reported treatment-related adverse events (AEs) include those observed with other KSP inhibitors, such as hematological AEs (thrombocytopenia, neutropenia, anemia, leukopenia), fatigue, mucositis and other gastro-intestinal AEs. Pts displayed linear PK, a low clearance and a moderate volume of distribution, with moderate-to-high inter-individual variability in PK parameters. The median terminal elimination half life is 65 hours. The preliminary efficacy signal as a single agent is encouraging with 2 partial responses (PR) observed to date per IMWG and EBMT criteria in a heavily pretreated population (23 evaluable pts). A bortezomib-refractory pt with 8 prior lines of therapy, including a tandem transplant, treated at 1 mg/m2/day of ARRY-520 obtained a PR after Cycle 6, with urine protein and kappa light chain levels continuing to decline over time. He remains on-study after 15 months of ARRY-520 treatment. A pt with 2 prior lines of therapy, including prior carfilzomib, has obtained a PR after Cycle 8 at 2 mg/m2/day of ARRY-520, and she is currently ongoing after 4.5 months on therapy. Fifteen pts had a best response of stable disease (SD), including 1 pt with a thus far unconfirmed minimal response, and 6 had progressive disease. A total of 10 pts (43%) achieved a PR or SD lasting > 12 weeks. Several additional pts have shown other evidence of clinical activity, with decrease in paraproteins, increase in hemoglobin levels and regression of plasmacytomas. The median number of cycles is 4 (range 1–28+). Treatment activity has not correlated with any baseline characteristics or disease parameters to date. Conclusions: : The selective KSP inhibitor ARRY-520 has been well tolerated, and shows promising signs of single agent clinical activity in heavily pretreated pts with RR MM. Prophylactic G-CSF has enabled higher doses to be tolerated. No cardiovascular or liver enzyme toxicity has been reported. Enrollment is ongoing at 1.75 mg/m2/day with G-CSF support, and a planned Phase 2 part of the study will be initiated as soon as the MTD is determined. Complete Phase 1 data will be disclosed at the time of the meeting. Disclosures: Shah: Celgene: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Millennium: Research Funding. Off Label Use: Revlimid (lenalidomide) in combination with dexamethasone is indicated for the treatment of multiple myeloma patients who have received at least one prior therapy. Zonder:Millennium: Consultancy, Myeloma and Amyloidosis Patient Day Symposium – Corporate support from multiple sponsors for a one-day educational event, Research Funding; Celgene:; Novartis:; Proteolix: . Weber:novartis-unpaid consultant: Consultancy; Merck- unpaid consultant: Consultancy; celgene- none for at least 2 years: Honoraria; millenium-none for 2 years: Honoraria; celgene, Millenium, Merck: Research Funding. Wang:Celgene: Research Funding; Onyx: Research Funding; Millenium: Research Funding; Novartis: Research Funding. Kaufman:Celgene: Consultancy, Honoraria, Research Funding; Millenium: Consultancy, Honoraria; Merck: Research Funding; Genzyme: Consultancy. Walker:Array Biopharma: Employment, Equity Ownership. Freeman:Array Biopharma: Employment, Equity Ownership. Rush:Array Biopharma: Employment, Equity Ownership. Ptaszynski:Array Biopharma: Consultancy. Lonial:Millennium, Celgene, Bristol-Myers Squibb, Novartis, Onyx: Advisory Board, Consultancy; Millennium, Celgene, Novartis, Onyx, Bristol-Myers Squibb: Research Funding.


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