First-in-human phase I/Ib multicenter, open-label dose escalation study to assess safety and tolerability of PMD-026 in patients with metastatic breast cancer with expansion in metastatic triple negative breast cancer

TPS1110

Background: Metastatic triple negative breast cancer (mTNBC) has a poor prognosis with limited durable treatment options. RSK (P90 ribosomal S6 kinase) is a signaling protein at the convergence point of PDK-1 and MAPK signaling pathways. RSK1-3 phosphorylates transcription factors, including Y-box binding protein-1 (YB-1), thereby inducing drug resistance and cancer growth genes. Phosphorylated YB-1 is involved in tumor cell survival, proliferation, and drug resistance. In human breast tumor samples, RSK2 protein is expressed across all breast cancer subtypes (TNBC, ER+ and HER2+) and is associated with poor overall survival. Expression of RSK2 is found in approximately 87% of mTNBC tumors and of those tumors approximately 41% have very high expression of RSK2. PMD-026 is a potent, oral, small molecule RSK inhibitor with high selectivity for RSK2. Preclinical in vivo studies have demonstrated activity both as a single agent and in combination with standard of care therapies. Further, a CAP/CLIA certified IHC method has been developed with Roche to determine tumor expression of RSK2. Methods: This single-arm, open-label, first-in-human, phase I/Ib study evaluates the safety and efficacy of single agent PMD-026 in patients with metastatic breast cancer for whom standard therapies are no longer effective. During dose escalation, the study utilizes an accelerated titration design with single patient cohorts until the occurrence of DLT or Grade 2+ toxicity; then reverts to 3+3 design to define the maximally tolerated dose (MTD) and recommended phase II dose (RP2D). The dose expansion portion will enroll approximately 20 patients with mTNBC. Patients are dosed orally once daily in 21-day cycles with measures to adapt the dosing schedule based on the pharmacokinetic (PK) data, as needed. Tumor tissue is required for all enrolled patients; RSK2 expression will be retrospectively correlated with clinical outcomes. The primary objectives are to determine safety and tolerability of PMD-026, determine the MTD, define a RP2D, and assess anti-tumor activity of PMD-026 in patients with TNBC. Secondary objectives are to evaluate PK, time to response, mTNBC subtyping using NanoString, and duration of response of PMD-026. To date, cohorts 1 and 2 have been completed without DLT. Enrollment to cohort 3 began in January 2020. Clinical trial information: NCT04115306 .

Safety and efficacy of pyrotinib in patients with NSCLC and other advanced solid tumors with activating HER2 alterations: A phase I basket trial

3510

Background: Pyrotinib is a potent, irreversible tyrosine kinase inhibitor (TKI) that blocks signal transduction through the erythroblastic leukemia viral oncogene homolog (erbB) receptors, which has previously demonstrated promising antitumor activity in patients (pts) with breast cancers. We studied the safety and efficacy of pyrotinib in pts with non-small cell lung cancer (NSCLC) and other solid tumors with activating human epidermal growth factor receptor 2 ( HER2, ERBB2) alterations. Methods: This is an open-label, multicenter phase 1 dose expansion basket trial of pyrotinib given 400mg oral daily at 28-day cycles. Expansion cohorts included pts with HER2-mutant NSCLC and advanced solid tumors with HER2 mutation or amplification. HER2 testing was conducted using next generation sequencing or fluorescence in situ hybridization. Primary endpoints included toxicities as evaluated by NCI CTCAE v5.0, and overall response rate (ORR) as evaluated by RECIST v1.1. Secondary objectives included progression-free survival (PFS). Results: A total of 62 pts were enrolled. The median age was 67 (range 40 – 86 years), 61% were female and the median lines of prior systemic therapy was 3 (range 1-11). There were no treatment related deaths. The most common adverse events were diarrhea (96.8%), nausea (82.3%) and vomiting (41.9%). The only ≥ grade 3 treatment related toxicity was diarrhea (24.2%). Prophylactic anti-diarrhea treatment was introduced to facilitate continuation of pyrotinib. At the Jan 13, 2020 cut-off, 24 pts with HER2-mutant NSCLC (20, i.e. 65% of which were the A775_G776insYVMA mutation) and 18 pts with HER2-mutant or amplified solid tumors completed end of Cycle 2 imaging scan and were evaluable for tumor responses. The ORR was 19% (8/42, 95% CI 7-31%); confirmed responses include a complete response (CR) and 3 partial responses (PRs) in HER2-mutant NSCLC, and 4 PRs in HER2-amplified cholangiocarcinoma, ovarian, endometrial and salivary gland carcinomas. There were 7 stable disease ≥ 6 months. Median progression-free survival was 5.4 months (95% CI 4.4-7.3). Conclusions: Pyrotinib demonstrated a manageable safety profile and encouraging efficacy in pts with heavily pre-treated HER2-mutant NSCLC. Furthermore, it is the first TKI to produce durable responses in pts with HER2-amplified biliary tract, ovarian, endometrial and salivary gland cancers. These results warrant further clinical development of pyrotinib. Clinical trial information: NCT02500199 .

BT5528-100 phase I/II study of the safety, pharmacokinetics, and preliminary clinical activity of BT5528 in patients with advanced malignancies associated with EphA2 expression

TPS3655

Background: BT5528 is a Bicycle Toxin Conjugate (BTC), comprising a bicyclic peptide targeting the tumor antigen EphA2, linked to a cytotoxin (monomethyl auristatin E [MMAE]) via a tumor microenvironment cleavable linker. Bicycles are a novel class of chemically synthesized constrained peptides, developed by Bicycle Therapeutics. EphA2 is reported to be overexpressed in a range of solid tumors, contributes to oncogenesis, tumor-associated angiogenesis and metastasis. Intracellular EphA2 signaling converges on pathways that are integral to cell growth, proliferation, migration and invasion. Increased EphA2 expression has been identified as a resistance mechanism to EGFR Tyrosine Kinase Inhibitor based therapy. BT5528 mechanism of action is dependent on tumor penetration, target binding and release of MMAE toxin payload. BTCs offer advantages over antibody-toxin conjugates exhibiting rapid penetration of dense tumors and decreased extra-tumor exposure. BT5528 exhibited a favorable preclinical profile supporting the initiation of a first-in-human study to investigate safety and efficacy of BT5528 in indications with evidence of EphA2 expression including non-small-cell lung cancer (NSCLC), ovarian cancer, triple-negative breast cancer (TNBC), gastric/upper gastrointestinal (GI), pancreatic and urothelial cancers. Methods: BT5528-100 (NCT04180371) is a Ph I/II study to evaluate safety and tolerability of weekly BT5528 alone and in combination with Q4W nivolumab. Each dose escalation utilizes a 3+3 design which converts to a Bayesian design to determine MTD or MAD and RP2D for BT5528 with and without nivolumab. Eligible patients must have advanced solid tumors associated with EphA2 expression which have recurred after exhausting standard treatment options. Patients must have available tumor tissue and acceptable hematologic and organ function, with exclusions for uncontrolled brain metastases, thromboembolic events, bleeding disorders, uncontrolled hypertension, CYP3A4 inhibitors/inducers or, for the nivolumab cohorts, autoimmune disease. On-study tumor and blood samples will be collected for biomarker evaluations including tumor EphA2 expression, ADA, and candidate response biomarkers for BT5528 alone and combination with nivolumab. Pharmacokinetic data will be reported for C1D1 and D15 for BT5528 and MMAE. The expansion phase will enroll specific tumor types to evaluate clinical activity of BT5528. Enrollment is ongoing. Clinical trial information: NCT04180371 .

MEDI3726, a prostate-specific membrane antigen (PSMA)-targeted antibody-drug conjugate (ADC) in mCRPC after failure of abiraterone or enzalutamide

99

Background: MEDI3726 is an ADC targeting PSMA. Once bound to PSMA and internalized, the released pyrrolobenzodiazepine dimer toxin crosslinks DNA and triggers cell death. This phase 1 study evaluated the safety and efficacy of MEDI3726 in mCRPC after failure of abiraterone and/or enzalutamide and a taxane-based therapy. Methods: The starting dose was 0.015 mg/kg MEDI3726 IV Q3W until disease progression or unacceptable toxicity. Dose escalation used a modified toxicity probability interval algorithm (mTPI). The primary objectives were safety, adverse events (AEs) and dose-limiting toxicities (DLTs) and to determine the maximum tolerated (MTD) or administered (MAD) dose. Secondary objectives included antitumor activity, pharmacokinetics and immunogenicity. The endpoint for activity was composite response: confirmed response by RECIST v1.1, and/or PSA decrease of ≥ 50% after ≥ 12 wks, and/or confirmed conversion in circulating tumor cell count, defined as a decrease from ≥ 5 to < 5 cells/7.5 mL. Efficacy analyses were based on Prostate Working Group Criteria. Mutational profiles were evaluated in ctDNA. Results: As of Sept 27 2019, 33 pts received MEDI3726. Median age was 71.0 yr. Median number of prior regimens was 4. Median follow-up was 5.4 mo. Drug-related AEs occurred in 30 (90.9%), being grade 3/4 in 15 (45.5%), serious in 11 (33.3%) and causing discontinuation in 13 (39.4%). There were no drug-related deaths. One pt at 0.3 mg/kg had a DLT of Grade 3 thrombocytopenia. No MTD was identified per mTPI; the MAD was 0.3 mg/kg. MEDI3726 had nonlinear PK with a short t1/2 (0.3–2 d). Three pts (15.8%) at baseline and 6 (33.3%) post-baseline had antidrug antibodies, with no correlation to PK exposure. Composite response rate across all doses was 2/33 (6.1%). Time to response was 0.3 mo; duration of response was 1.8–3.8 mo. Median progression-free survival was 3.9 mo and median overall survival was 10.6 mo. Conclusions: An MTD was not identified, but drug-related AEs (skin toxicities and effusions) prevented raising the dose over 0.3 mg/kg and limited the number of cycles. Responses were seen at higher doses, but were not durable as pts discontinued due to drug-related AEs. Clinical trial information: NCT02991911.

Phase I dose escalation of H3B-6545, a first-in-class highly Selective ERα Covalent Antagonist (SERCA), in women with ER-positive, HER2-negative breast cancer (HR+ BC)

1059

Background: H3B-6545 inactivates both wild-type and mutant ERα by targeting cysteine 530 and enforcing a unique antagonist conformation. Methods: Women with locally advanced or metastatic HR+ BC are treated (tx) with H3B-6545 administered once daily orally over a 28 day cycle after progression on at least one hormonal therapy and at least one additional therapy/regimen. Dose escalation uses a 3+3 design with the option to backfill previously cleared doses and allows for intrapatient dose escalation. This phase 1 explores the safety, pharmacokinetics and pharmacodynamics of H3B-6545 in women with HR+ BC to identify the recommended Phase 2 dose. Results: As of 10-Dec-2018, 32 pts have been tx with H3B-6545 at doses of 100 to 450 mg/day; 97% had prior tx with a CDK4/6 inhibitor and 56% had received ≥3 lines of prior anti-cancer therapy. No dose-limiting toxicities and only one Grade 3 treatment related adverse event (TRAE) have been observed (lymphocyte count decrease). The most common (≥10%) TRAEs include asymptomatic sinus bradycardia, diarrhea, nausea, fatigue, anemia, decreased appetite, and hot flush. H3B-6545 was rapidly absorbed with a tmax of 2-4 h. Plasma concentration increased with dose from 100 to 450 mg, and was similar on C1D1 and C1D15. Consistent with the H3B-6545 mechanism of action and preclinical data, H3B-6545 inhibits ER target gene expression and shows a 50% decrease in Ki67 levels across all dose levels post-tx. ESR1 (60%) and PIK3CA (34%) mutations were detected in plasma at baseline and changes in mutant allele frequencies show correlation in response to tx. Stable disease was observed in 15 pts (47%) and 34% of pts completed at least 6 months of tx. Partial responses (PRs) were observed in 3 pts: 1 pt (mutant) received 2 prior lines of therapy and 2 pts (1 mutant and 1 wild-type) received >5 prior lines of therapy including fulvestrant and capecitabine; all 3 pts received a prior CDK4/6 inhibitor. Conclusions: H3B-6545 has been well-tolerated up to the 450 mg dose level with early signs of single-agent anti-tumor activity in a post CDK4/6 setting. Dose escalation continues in pts with advanced HR+ BC. Clinical trial information: NCT03250676.

Molecular characterization and monitoring of patient ctDNA in phase I study of H3B-6545 in ER+ MBC

1052

Background: Because of lack of effective treatment in endocrine resistant metastatic breast cancer (MBC), we developed H3B-6545, a novel selective ERa covalent antagonist, capable of irreversibly inactivating both wild-type and mutant ERa. The aims of this study are to 1) characterize hotspot mutation profiles in heavily pretreated MBC and correlate ESR1, PIK3CA and AKT1 mutations in plasma vs tumor tissue 2) determine if mutations in ESR1 or PIK3CA predict response to H3B-6545 and 3) evaluate if longitudinal tracking of ctDNA correlates with response to H3B-6545. Methods: Fresh plasma samples were collected at baseline (predose), cycle 1 day 15 (C1D15), C2D1, C3D1 and every 8 weeks thereafter with a final sample collection at disease progression. At baseline, BEAMing digital PCR was used to evaluate hotspot mutations in ESR1, PIK3CA and AKT1. Patient specific ctDNA mutations were subsequently monitored by ddPCR. Baseline tumor biopsies were subjected to a targeted Next Generation Sequencing (NGS) panel to identify hotspot mutations. Results: In 77% of patients (30/39), mutations were detected at baseline by the BEAMing assay and of those, 21/39, 16/39 and 3/39 had mutations in ESR1, PIK3CA and AKT1, respectively. 20% (9/39) of patients exhibited co-mutations in ESR1 and PIK3CA. In 60% (9/15) of patients, DNA mutations identified by the plasma BEAMing assay were also detected in the tumor biopsy whereas; DNA mutations found in tissue were also detected in plasma in 86% (12/14) of cases. Serial ctDNA monitoring revealed that in patients with confirmed partial responses (3/3), ctDNA levels were undetectable by C2D1. In contrast, ctDNA levels increased from baseline in 3/4 patients with progressive disease. Exploration of ctDNA ratios (day 15/baseline and day 30/baseline) and correlations of PIK3CA and ESR1 mutations with response to H3B-6545 will be presented. Conclusions: ctDNA is a reliable sample type for assessing ESR1, PIK3CA, and AKT1 mutations in MBC, overcoming the challenges of obtaining biopsies in the metastatic setting. In addition, ctDNA dynamics may be a useful tool to monitor the efficacy of H3B-6545. Clinical trial information: NCT03250676.

A phase I, open label, multicenter dose escalation study of AZD2811 nanoparticle in patients with advanced solid tumors

3098

Background: Aurora kinase B (AURKB) represents a potential target for therapy in solid and hematological malignancies. AURKB inhibitor AZD1152 (barasertib) was previously investigated in solid tumor pts in a phase I setting. AZD2811-nanoparticle (np) is a novel, encapsulated slow release AURKB inhibitor offering several advantages over AZD1152 (Ashton S et al., Sci Transl Med 2016). We report the completed dose-escalation safety, pharmacokinetics (PK), preliminary activity and defined maximum tolerated dose (MTD) of AZD2811-np in pts with advanced solid tumors (NCT02579226). Methods: Adult pts with advanced solid tumors received AZD2811-np IV on Day 1 (D1) and 4 (D4) Q4 week (wk) in six cohorts 15-200 mg/infusion without the use of g-csf in cycle 1. D1 Q4wk and Q3wk schedules were investigated up to 600 mg/infusion (including cohorts with mandatory g-csf prophylaxis on day 8). A standard 3+3 design was used. PK was assessed in cycle 1. Results: 50 pts were recruited into 12 cohorts. D1, D4 Q4wk schedule: 24 pts (15, 25,38, 50, 100 mg/infusion (n=3/cohort), 200 mg/infusion (n=9)). All cohorts were tolerated. Transient grade 4 neutropenia was observed in 7/9 pts at 200 mg/infusion, including 1 DLT (gr4 > 7 days) D1 Q4wk: 200 mg(n=3) was tolerated. D1 Q3wk: 23 pts were evaluated (200/400 mg (n=3,7), and 400/600/500 mg with mandatory g-csf (n=3/5/6)). 400 mg without g-csf was not tolerated (1 gr3 mucosal inflammation & 1 gr4 neutropenia > 7 days). 600 mg with g-csf was not tolerated (gr3 febrile neutropenia & gr3 fatigue). 25/50 pts experienced AE ≥gr 3 (21 considered AZD2811-np-related, 19 neutropenia-related, no deaths within-DLT period). AZD2811-np caused transient gr1/2 fatigue, nausea, diarrhoea and mucosal inflammation. AZD2811 total blood PK appears dose proportional with a t1/2 of 30-50 hours irrespective of schedule. Released AZD2811 concentrations ~1% of total. 14 pts (28%) had disease stabilisation. 1 prostate ca. pt had a confirmed partial response (PR) (continued tx to 451 days). Conclusions: The MTD for AZD2811-np is 500 mg D1 Q3wk. AZD2811-np is now being investigated in a small cell lung cancer expansion. Clinical trial information: NCT02579226.

First-in-human study of AZD5153, a small molecule inhibitor of bromodomain protein 4 (BRD4), in patients (pts) with relapsed/refractory (RR) malignant solid tumor and lymphoma: Preliminary data

3085

Background: BRD4 is a bromodomain and extraterminal (BET) protein that regulates oncogenic programs by modifying gene transcription and additional mechanisms. AZD5153 is a novel, reversible BRD4 inhibitor with bivalent mechanism of action and enhanced antitumor activity in preclinical models. This phase 1, multicenter, dose escalation study (NCT03205176) assesses AZD5153’s safety, pharmacokinetics (PK), and pharmacodynamics (PD). We report here preliminary, unvalidated data from AZD5153 monotherapy in pts with RR solid tumor, including lymphoma. Methods: Adult pts received oral AZD5153 QD/BID to determine the MTD. During dose escalation, a continual reassessment model was used to estimate toxicity and all final decisions were made by the Safety Review Committee. PK and PD were characterized using standard methods. Results: As of 1 Nov 2018, 28 pts (78.6% female, median age 66.5 y) were treated in 7 cohorts: 2 mg QD (3 pts), 5 mg QD (3 pts), 10 mg QD (3 pts), 10 mg BID (5 pts), 15 mg BID (4 pts), 20 mg BID (7 pts), and 30 mg QD (3 pts). Treatment was ongoing in 8 pts at data cut-off. Safety findings showed 50% of pts experienced treatment-related AEs. 25% of pts experienced treatment-related Grade ≥3 AEs, which were thrombocytopenia and fatigue (7.1% each), and anemia, diarrhea, and platelet count decreased (3.6% each). SAEs were observed in 25% of pts; none of the SAEs was attributable to AZD5153 alone. Dose-limiting toxicities of thrombocytopenia (1 pt) and diarrhea with herpetic rash leading to discontinuation (1 pt) occurred at 20 mg BID. 53.6% of pts discontinued due to disease progression. Total median treatment duration was 1.3 mo (range up to 8.9 mos). Dose proportional increase in Cmax and AUC were observed across the dose range tested. Tmax ranged from 0.5 to 3 h and t1/2 was 6 h. Dose-dependent changes in expression of target genes (eg, HEXIM1, HIST2H2BF, CD274, and CCR2) and platelet counts were observed in the peripheral blood. Conclusions: AZD5153 monotherapy is safe and tolerated at doses up to 30 mg QD and 15 mg BID. Linear increase in PK was observed. Additional safety and efficacy updates will be reported at the annual meeting. Clinical trial information: NCT03205176.

A phase Ib study of prexasertib, a checkpoint kinase (CHK1) inhibitor, and LY3023414, a dual inhibitor of class I phosphatidylinositol 3-kinase (PI3K) and the mammalian target of rapamycin (mTOR) in patients with advanced solid tumors

3091

Background: Prexasertib inhibits CHK1, a kinase involved in DNA repair and replication. LY3023414 inhibits PI3K/mTOR signaling, implicated in the development of malignant disease. Prexasertib + LY3023414 has resulted in enhanced antitumor activity in triple negative breast cancer (TNBC) in vitro models. Methods: This Phase 1b study in patients (pts) with solid tumors assessed escalating doses of prexasertib (60-105 mg/m2 IV every 14 days [q14d]) and LY3023414 (100-200 mg orally twice daily [BID]). Dose escalation ceased once the maximum tolerated dose of each monotherapy was reached. An initial expansion cohort (Arm E) explored prexasertib 105 mg/m2 q14d + LY3023414 200 mg BID. Subsequent expansion cohorts evaluated prexasertib 105 mg/m2 q14d + LY3023414 150 mg BID in pts with solid tumors with PIK3CA mutations (Arm E2) or TNBC (Arm E3). Results: Fifty pts were enrolled (escalation: n = 13; Arm E: n = 9; Arm E2: n = 15; Arm E3: n = 13). No dose-limiting toxicities (DLTs) were observed during escalation however DLT-equivalent toxicities were observed in 2 pts in Arm E (anemia, neutropenia, thrombocytopenia, oral mucositis, abdominal pain, fatigue). Due to toxicity, a reduced dose of LY3023414 (150 mg BID) was assessed in Arm E2/E3. In the 28 patients treated in Arms E2/E3, common treatment-related adverse events (any grade; grade ≥3) were: leukopenia/neutropenia (82%; 79%), thrombocytopenia (46%; 36%), nausea (46%; 0%), stomatitis (39%, 4%), vomiting (36%; 0%), and anemia (29%; 18%). Febrile neutropenia was reported in 25% of pts. Dose reductions in Arm E2/E3 were common. In escalation, 2 pts achieved a partial response (PR) and 3 pts achieved stable disease (SD). In Arm E, 78% of pts achieved SD. Of the pts evaluable at the time of data transfer, PRs were achieved in 1 pt with an unknown primary (Arm E2) and 2 pts with TNBC (Arm E3). Each agent’s pharmacokinetic profile was consistent with prior monotherapy data. Conclusions: Prexasertib + LY3023414 showed preliminary efficacy in heavily pretreated pts with solid tumors but was associated with toxicity, suggesting supportive care may be required. Clinical trial information: NCT02124148.

Open-label, multicenter, phase I study to assess safety and tolerability of adavosertib plus durvalumab in patients with advanced solid tumors

2562

Background: Adavosertib (AZD1775; A) is a highly selective inhibitor of WEE1. This Phase I study (NCT02617277) investigated a range of doses and schedules for oral A plus IV durvalumab (DV), a human monoclonal antibody targeting PD-L1, to determine the maximum tolerated dose (MTD) and recommended Phase II dose (RP2D) in patients (pts) with advanced solid tumors. Methods: Four 28-day schedules (Sch) were evaluated with pts receiving DV 1500 mg on day (d) 1 of each schedule (Table). Patients continued treatment if they showed clinical benefit in the absence of any discontinuation criteria. Pts received A monotherapy for PK analysis prior to the start of combination therapy in Sch B, C (d –7 to –5) and D (d –9 to –5). MTD was determined using a 3+3 dose-escalation cohort design. Predefined dose-limiting toxicities (DLTs) were evaluated during the first cycle of study treatment. Results: 54 pts received A (most common primary tumor sites: colon, 19%; lung, 13%; breast, 11%). The most common grade ≥3 AEs were fatigue (15%), diarrhea (11%) and nausea (9%). DLTs were nausea (n = 2) and diarrhea (n = 1). 7 pts (13%) had A-related SAEs, including reversible and confounded drug-induced liver injury (Sch B 125 mg and Sch C; 1 each). Disease control rate (DCR) for the total cohort was 36%. Preliminary PK at 150 mg BID suggests adequate coverage for cell kill activity and no drug–drug interaction. Conclusions: The MTD/RP2D was A 150 mg BID (3 d on, 4 d off; treatment d 15–17, 22–24) with DV 1500 mg (d 1 Q4W); safety profile was considered acceptable. Preliminary evidence of antitumor activity was observed. Clinical trial information: NCT02617277. [Table: see text]

Abstract LB-B25: Preliminary phase I data comparing HuMab-5B1 (MVT-5873), a monoclonal antibody targeting sLea, as a single agent and in combination with first line nab-paclitaxel and gemcitabine in patients with CA19-9 positive pancreatic cancer

IntroductionMVT-5873, a fully human IgG1 monoclonal antibody (mAb), targets sialyl Lewis A (sLea), an epitope on CA19-9. CA19-9 is expressed in pancreatic (PDAC) and other GI cancers, plays a role in tumor adhesion and metastasis, and is a marker of an aggressive tumor phenotype. MVT-5873 is active as a single agent and in combination with nab-paclitaxel (nab-P) and gemcitabine (gem) in murine xenografts. MethodsSingle agent: for each 28-day treatment cycle, MVT-5873 was given IV every second week (Group 1) or weekly (Group 2) at doses ranging from 1 to 3 mg/kg. Combination with nab-P and gem: for each 28-day treatment cycle MVT-5873 was administered IV weekly (1.0mg/kg or 0.125mg/kg) followed by IV infusion of 125 mg/m2 of nab-P and then 1000mg/m2 gem, on day 1, 8 and 15 (Group 3). Eligible patients had recurrent progressive (single agent) or newly diagnosed (combination), locally-advanced or metastatic PDAC or other CA19-9+ malignancy and ECOG PS ≤1. Dose escalation followed a standard 3+3 design with a 10 patient expansion at the maximally tolerated dose (MTD). Trial endpoints include safety, MTD, dose limiting toxicities (DLT), pharmacokinetics (PK) and efficacy. Exploratory endpoints include changes in serum CA19-9 levels.ResultsAs of 7-September-2017, data are available for single agent N=32 in Groups 1 (N=9) and 2 (N=23) at 1, 2, 2.5 and 3 mg/kg and combination Group 3 (N=6) at 1.0 and 0.125mg/kg. DLTs of transient grade 3 elevations in AST, ALT, and total bilirubin were encountered in the single agent groups at 2, 2.5 and 3mg/kg in both single agent groups and in the combination group at 1mg/kg. Single agent liver function laboratory abnormalities typically emerged and resolved within a week of dosing although they were more persistent in the combination treated patients. Other toxicities associated with all groups included low grade GI toxicity (abdominal pain/cramps/diarrhea/nausea) and infusion reactions. Infusion reactions were mitigated with pre-medications and an increase in the infusion time. Combination DLTs for MVT-5873 at 1mg/kg included AST, ALT, and bilirubin elevations as well as neutropenia and pneumonitis resulted in significant dose de-escalation. MVT-5873 dosed at 0.125 mg/kg in combination was generally well tolerated. Single agent activity included SD of &gt;4 months in 5 of 32 of patients with an MTD established at 1 mg/kg. Combination activity at 0.125 mg/kg MVT-5873 with nab-P/gem included 2 PRs and 1 SD in 3 patients. Interestingly, sustained suppression below ULN of CA19-9 levels was observed in 3 of the 6 patients in the combination arm and &gt;95% CA19-9 reduction at the 0.125mg/kg combination dose. Dose escalation in this arm is in progress, and updated safety, PK/PD, and efficacy data will be presented.ConclusionsSingle agent MVT-5873 appears safe and tolerable at biologically active doses. DLTs included reversible liver function abnormalities. Determination of the MTD in combination with first line nab-P/gem is underway and preliminary response data are encouraging. Overall, the safety profile, efficacy, and reductions in serum CA19-9 levels over time support further development of MVT-5873 in this indication both as a single agent and in combination.

Citation Format: Eileen Mary O'Reilly, Judy Sing-Zan Wang, Kenneth H. Yu, Maeve Aine Lowery, Anna M. Varghese, Johanna C. Bendell, Erkut Hasan Borazanci, Hayley Estrella, Kimberly Fowler, Mariella Hoskins, Stephanie Bussen, Teresa J. Melink, Christine M. Kearns, H Toni Jun, Paul W. Maffuid, John C. Gutheil, Todd Michael Bauer. Preliminary phase I data comparing HuMab-5B1 (MVT-5873), a monoclonal antibody targeting sLea, as a single agent and in combination with first line nab-paclitaxel and gemcitabine in patients with CA19-9 positive pancreatic cancer [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2017 Oct 26-30; Philadelphia, PA. Philadelphia (PA): AACR; Mol Cancer Ther 2018;17(1 Suppl):Abstract nr LB-B25.

Phase I trial of a novel stapled peptide ALRN-6924 disrupting MDMX- and MDM2-mediated inhibition of WT p53 in patients with solid tumors and lymphomas

2505

Background: ALRN-6924 is a cell-penetrating stapled alpha-helical peptide designed to equipotently disrupt the interaction between the p53 tumor suppressor protein and its endogenous inhibitors, murine double minute X (MDMX) and 2 (MDM2). For TP53 wild-type (WT) tumors, pharmacological disruption of this interaction offers a means to restore p53-dependent cell cycle arrest and apoptosis, resulting in antitumor efficacy via a novel mechanism. Methods: The study evaluated safety, PK, PD and anti-tumor effects of ALRN-6924 in patients (pts) with advanced solid tumors or lymphomas in a standard 3+3 design. Pts received ALRN-6924 IV once weekly for 3 consecutive wks on a 28-day cycle (arm A), or 2/wk for 2 consecutive wks on a 21-day cycle (arm B). Results: As of Dec 2016, 69 pts were enrolled with median age 61 yrs (25-78). Pts received a median of 2 (1-19) cycles in arm A [0.16-4.4 mg/kg] and 3 (1-19) cycles in arm B [0.32-2.7 mg/kg]. ALRN-6924 showed a t1/2 of 5.5 hours, dose-dependent PK, and an increase in serum macrophage inhibitory cytokine-1. Treatment-related AEs seen in 96% of pts were primarily grade 1 and 2; most frequent were GI side effects, fatigue, anemia, and headache. DLTs were G3 fatigue at 3.1 mg/kg, and G3 hypotension, G3 alkaline phosphatase elevation, G3 anemia and G4 neutropenia at 4.4 mg/kg all in 5 pts in arm A. No G3/4 thrombocytopenia was observed. All DLTs resolved with dose hold. Infusion-related reactions were seen in 7 pts, with 3 treatment discontinuations. The RP2D was determined to be at MTD: 3.1 mg/kg QW for 3 wks every 28 days. In 55 pts evaluable for efficacy, disease control rate (DCR) was 45%, including 2 CR (Peripheral T-cell Lymphoma [PTCL], Merkel Cell Carcinoma), 2 PRs (Colorectal Cancer, Liposarcoma) and 21 pts with SD. In WT TP53 pts who initiated ALRN-6924 at ≥0.8 mg/kg, DCR was 57%. 9 pts remain on treatment post data cutoff including 3 pts exceeding 1 year of treatment. Conclusions: ALRN-6924 was well tolerated and demonstrated intriguing anti-tumor activity in this first-in-human phase I trial. An expansion phase IIa cohort in PTCL opened in August 2016 using 3.1 mg/kg (arm A) and is currently enrolling. Clinical trial information: NCT02264613.

A phase I, open-label, first-time-in-patient dose escalation and expansion study to assess the safety, tolerability, and pharmacokinetics of nanoparticle encapsulated Aurora B kinase inhibitor AZD2811 in patients with advanced solid tumours

TPS2608

Background: Aurora kinase B performs key roles in the regulation of the cell cycle and represents a potential target for anticancer therapy. AZD2811, formerly designated AZD1152 hydroxy-quinazoline pyrazole anilide (AZD1152 hQPA), is a potent and selective inhibitor of Aurora B kinase activity and has been incorporated into a polymer nanoparticle carrier for intravenous (IV) administration. The phosphate pro-drug of AZD2811, known as AZD1152 (barasertib), reached Phase II of clinical development as a continuous IV infusion. While promising efficacy was seen with barasertib in elderly acute myeloid leukaemia (AML) patients ( Kantarjian HG et al., Cancer 2013;119:2611-19), continuous intravenous drug delivery precluded subsequent development in this disease setting and there were limited clinical responses in solid tumour patients due to dose-limiting myelotoxicity. AZD2811 nanoparticle has been designed to overcome these issues. Methods: Patients with relapsed advanced solid malignancies with no standard treatments are eligible for the part A dose escalation. Primary endpoint is to determine the maximum tolerated dose of AZD2811 nanoparticle using a 3+3 design. Patients with refractory/relapsed small cell lung cancer (SCLC) will be eligible for the part B expansion, where the safety, PK and anti-tumour activity of AZD2811 nanoparticle will be assessed as monotherapy and in combination with chemotherapy. Study enrolment is ongoing. Clinical trial information: NCT02579226.

A phase 1/1b multicenter, open-label, dose escalation and dose expansion study to evaluate the safety, pharmacokinetics, immunogenicity, and antitumor activity of MEDI3726 in patients with metastatic, castration-resistant prostate cancer who have received prior treatment with abiraterone or enzalutamide

TPS5088

Background: Therapeutic advances have recently been achieved for patients with metastatic, castration-resistant prostate cancer (mCRPC) due to abiraterone acetate (ABI) and enzalutamide (ENZ). However, virtually all patients with mCRPC eventually progress in their disease, and further treatment options are limited. Prostate-specific membrane antigen (PSMA) is highly expressed in nearly all prostate cancers, and its expression is highest in mCRPC. MEDI3726 is an antibody-drug conjugate composed of anti-PSMA antibody derived from J591, site-specifically conjugated to the cytotoxic, DNA cross-linking, pyrrolobenzodiazepine dimer. MEDI3726 has demonstrated potent and specific in vitro and in vivo antitumor activity in human prostate cancer-derived preclinical models with different expression levels of PSMA. Methods: This is a first-in-human, phase 1/1b, multicenter, open-label, dose escalation and dose expansion study in patients who have received prior treatment with ABI or ENZ, with or without prior taxane-based chemotherapy in the mCRPC setting (NCT02991911). The primary objectives are to assess safety and tolerability, describe dose-limiting toxicities, and determine the maximum tolerated dose or maximum administered dose of MEDI3726. The secondary objectives are to evaluate MEDI3726 for its antitumor activity (based on a composite response according to RECIST Version 1.1, a reduction in prostate-specific antigen level of 50% or more compared to baseline, or a conversion in the circulating tumor cell count [defined as a reduction from ≥5 cells/7.5 mL blood to < 5 cells/7.5 mL blood]), safety and tolerability in combination with ENZ, pharmacokinetics alone and in combination with ENZ, and immunogenicity. Recruitment is ongoing for this study, which has an estimated total target enrollment of 224 patients. Clinical trial information: NCT02991911.

Single agent HuMab-5B1 (MVT-5873), a monoclonal antibody targeting sLea, in patients with pancreatic cancer and other CA19-9 positive malignancies

4110

Background: MVT-5873, a fully human IgG1 monoclonal antibody (mAb), targets sialyl Lewis A (sLea), an epitope on CA19-9. CA19-9 is expressed in pancreatic (PDAC) and other GI cancers, plays a role in tumor adhesion and metastasis, and is a marker of an aggressive tumor phenotype. MVT-5873 is active as a single agent and with chemotherapy in murine xenografts. Methods: MVT-5873 was given IV every other week (Group 1) or weekly (Group 2). Eligible patients had progressive, locally-advanced or metastatic PDAC or other CA19-9+ malignancy and ECOG PS ≤1. Dose escalation followed a 3+3 design with a 10 patient expansion at MTD. Endpoints include safety, MTD, pharmacokinetics (PK) and efficacy. Exploratory endpoints include changes in serum CA19-9 levels. Results: As of 2-Feb 2017, data are available from N = 25 in Groups 1 (N = 9) and 2 (N = 16) at doses ranging from 1 to 3 mg/kg. Dose limiting toxicities of transient grade 3 elevations in AST, ALT, and total bilirubin were encountered at 3 mg/kg in both groups. Liver function laboratory abnormalities typically emerged and resolved within a week of dosing without significant clinical sequelae. Of toxicities deemed possibly related, most were low grade and included GI toxicity (abdominal pain/cramps/diarrhea/nausea) and infusion reactions. Infusion reactions were mitigated by using pre-medications and decreasing the infusion rate. Initial PK data demonstrate initial (20 hours) and terminal (211 hours) half-lives, comparable to other mAbs. Stable disease of > 4 months was observed in 24% of patients. CA19-9 levels were measured pre- and post-dose with each treatment. Immediate reductions showed dose-dependent reductions of up to 97% from baseline at 3 mg/kg. Downward trends of CA19-9 with successive doses were seen, with 48% and 22% of patients exhibiting ≥50% and ≥90% reductions in CA19-9 levels, respectively. Conclusions: Single agent MVT-5873 appears safe and tolerable at biologically active doses. DLTs included reversible serologic liver toxicity. The safety profile, efficacy, and reductions in serum CA19-9 levels over time support further development of MVT-5873 in this indication both as a single agent and in combination. Clinical trial information: NCT02672917.

A phase I study of investigational agent SGI-110 combined with irinotecan in previously treated metastatic colorectal cancer patients

TPS797

Background: Studies have suggested that epigenetic modifications may play a role in oncogenesis and acquired chemoresistance in certain cancers including colorectal cancer (CRC). Our preclinical data has shown that DNA hypermethylation may confer acquired chemoresistance, and that combining a hypomethylating agent can re-induce tumor sensitivity to irinotecan in CRC cell lines. We propose a phase I study to assess the safety and tolerability of SGI-110 with irinotecan therapy in metastatic colon cancer previously treated with irinotecan. This will be followed by a randomized phase II study to evaluate efficacy of the combination. Methods: We will enroll 12-22 patients at two institutions with metastatic colon adenocarcinoma previously treated with irinotecan to our phase I study. Dose escalation will be performed in a traditional 3+3 design, where patients receive SGI-110 30-45mg/m2 SQ days 1-5 in combination with irinotecan 125mg/m2 days 1, 8, and 15 (depending on the dose level) every 28 days, with or without G-CSF. Patients will be monitored for safety and tolerance with laboratory studies, clinical exam, and periodic CT scans to assess response to therapy. In addition, pharmacokinetic studies on peripheral blood and paired tumor biopsies will be obtained to assess for global demethylation and evaluation of biomarkers. Major eligibility criteria include measureable disease with accessibility for paired tumor biopsies, and prior treatment with irinotecan without limit on number of total therapies. Current Enrollment: Dose level 1 enrolled 6 patients and encountered 1 DLT following expansion for safety assessment. Dose level -1 enrolled 3 patients and encountered 2 DLTs, which has since prompted amendments for additional dose levels with modifications to scheduled growth factor support. Dose level -1G enrollment began in September 2014. Clinical trial information: NCT01896856.