A Phase I Study of the Pan-Notch Inhibitor CB-103 for Patients with Advanced Adenoid Cystic Carcinoma and Other Tumors

PURPOSE

CB-103 selectively inhibits the CSL-NICD (Notch intracellular domain) interaction leading to transcriptional downregulation of oncogenic Notch pathway activation. This dose-escalation/expansion study aimed to determine safety, pharmacokinetics, and preliminary antitumor activity.

EXPERIMENTAL DESIGN

Patients ≥18 years of age with selected advanced solid tumors [namely, adenoid cystic carcinoma (ACC)] and hematologic malignancies were eligible. CB-103 was dosed orally in cycles of 28 days at escalating doses until disease progression. Notch-activating mutations were required in a dose confirmatory cohort. Endpoints included dose-limiting toxicities (DLT), safety, tumor response, pharmacokinetics, and pharmacodynamics. Exploratory analyses focused on correlates of Notch and target gene expression.

RESULTS

Seventy-nine patients (64, 12 dose-escalation cohorts; 15, confirmatory cohort) enrolled with 54% receiving two or more lines of prior therapy. ACC was the dominant tumor type (40, 51%). Two DLTs were observed [elevated gamma-glutamyl transferase (GGT), visual change]; recommended phase II dose was declared as 500 mg twice daily (5 days on, 2 days off weekly). Grade 3-4 treatment-related adverse events occurred in 15 patients (19%), including elevated liver function tests (LFTs), anemia, and visual changes. Five (6%) discontinued drug for toxicity; with no drug-related deaths. There were no objective responses, but 37 (49%) had stable disease; including 23 of 40 (58%) patients with ACC. In the ACC cohort, median progression-free survival was 2.5 months [95% confidence interval (CI), 1.5-3.7] and median overall survival was 18.4 months (95% CI, 6.3-not reached).

CONCLUSIONS

CB-103 had a manageable safety profile and biological activity but limited clinical antitumor activity as monotherapy in this first-in-human study.

SIGNIFICANCE

CB-103 is a novel oral pan-Notch inhibitor that selectively blocks the CSL-NICD interaction leading to transcriptional downregulation of oncogenic Notch pathway activation. This first-in-human dose-escalation and -confirmation study aimed to determine the safety, pharmacokinetics, and preliminary antitumor efficacy of CB-103. We observed a favorable safety profile with good tolerability and biological activity but limited clinical single-agent antitumor activity. Some disease stabilization was observed among an aggressive NOTCH-mutant ACC type-I subgroup where prognosis is poor and therapies are critically needed. Peripheral downregulation of select Notch target gene levels was observed with escalating doses. Future studies exploring CB-103 should enrich for patients with NOTCH-mutant ACC and investigate rational combinatorial approaches in tumors where there is limited success with investigational or approved drugs.

Phase 1 study of CB-103, a novel first-in-class inhibitor of the CSL-NICD gene transcription factor complex in human cancers

3020

Background: CB-103 selectively inhibits the CSL-NICD interaction leading to down-regulation of CSL-NICD mediated oncogenic pathway activation downstream of NOTCH receptor/ligand signaling, and has shown potent anti-cancer activity as single agent and in combination with targeted/chemotherapies in preclinical models. The aim of this dose escalation/expansion phase 1/2a study is to assess safety, maximum tolerated dose (MTD) and recommended phase 2 dose (RP2D), preliminary activity, pharmacokinetics and pharmacodynamics of CB-103. Methods: Eligible were adult patients (pts) with advanced or recurrent selected solid tumors. Tumor tissue, where available, was retrospectively tested for NOTCH pathway activating mutations and surrogate tissues were evaluated for gene expression of related target genes. CB-103 was given orally in 28 days cycles at escalating doses until disease progression or toxicity. In a dose confirmatory cohort, NOTCH activation will be prospectively assessed to determine eligibility. Results: Forty-one pts (19 adenoid cystic carcinoma (ACC), 16 colorectal and 4 breast cancer, 2 prostate cancer) were assigned to increasing dose levels starting from 15mg once daily (OD). Median age was 55 years (range 25-76). Median number of prior lines of therapy was 2 (range 0-7). Thirty-two pts in 8 escalation groups completed the 28-day DLT window. One DLT (asymptomatic grade (G) 3 GGT increase) was observed at the highest dose (600mg). Related treatment emergent adverse events (AE) occurring in >10% of pts were nausea (24%), diarrhea (20%), dyspepsia (15%), fatigue (12%) and vision blurred (12%), all G 1/2. No discontinuations occurred due to treatment-related AEs. The MTD has not been reached. Several pts reported vision changes that improved over time and were fully reversible after stopping the drug. Median time on treatment for all pts was 52 days (range 5-249). Best response was stable disease (SD). For ACC pts, preliminary median PFS was 21.7 weeks (95% confidence interval (CI) 13.7-22.4 weeks) and disease control rate (DCR) was 79% at week 8 and 58 % at week 20. Three pts with ACC harboring activating NOTCH alterations had radiologically confirmed stable disease (SD) > 6 months. Importantly, in 3 pts with NOTCH positive disease a temporary stop of tumor growth was observed. One pt showed a reduction in size of a liver lesion up to 25% before progression due to new lesions. Mechanistically, strong on-treatment downregulation of NOTCH target genes was observed. The dose of 600mg CB-103 OD was declared the RP2D. Conclusions: CB-103 is the first drug to effectively control the CSL-NICD transcription complex. CB-103 is well tolerated in pts with advanced tumors and, as expected on the basis of mechanistic studies, in the absence of the typical toxicities associated with Notch targeting GSIs or mABs. The RP2D has been established for advancing clinical development into phase 2. Clinical trial information: NCT03422679.

A phase Ib study to evaluate the oral selective estrogen receptor degrader GDC-9545 alone or combined with palbociclib in metastatic ER-positive HER2-negative breast cancer

1023

Background: GDC-9545 is a potent, orally available, selective estrogen receptor degrader developed for the treatment of ER-positive (ER+) breast cancer alone or combined with CDK4/6 inhibitors. A first-in-human study evaluated 10-250 mg GDC-9545; tolerability, pharmacokinetic (PK), pharmacodynamic (PD), and clinical results support expansion cohorts at ≥30 mg (Jhaveri et al., 2019). Methods: This study evaluated PK, PD, and efficacy of GDC-9545 alone and combined with palbociclib, ± LHRH agonist. Eligible patients (pts) had ER+ (HER2-) metastatic breast cancer (MBC) with ≤ 2 prior therapies in the advanced or metastatic setting. No prior treatment with CDK4/6 inhibitor was allowed in pts receiving palbociclib. Results: Eight-five pts were enrolled in 2 cohorts: GDC-9545 100 mg given once daily ± LHRH agonist (Cohort A), and GDC-9545 100 mg +125 mg palbociclib on a 21 day on/7 day off schedule ± LHRH agonist (Cohort B). Of the 39 pts in Cohort A, adverse events (AE) occurring in ≥10% of pts were fatigue, cough, back pain, pain in extremity, and arthralgia. Related AEs were generally Grade (G) 1-2; there were 3 related G3 AEs of fatigue, transaminase increased, and diarrhea. Two pts had GDC-9545 reduced, one due to G3 diarrhea and another due to G3 transaminitis. Of the 46 pts in Cohort B, AEs in ≥10% of pts were neutropenia, fatigue, bradycardia, diarrhea, constipation, dizziness, nausea, anemia, asthenia, thrombocytopenia, pruritus, and visual impairment. Twenty-six (57%) pts had G≥3 AEs. G≥3 neutropenia was reported in 23 (50%) pts. One pt had palbociclib reduced due to G3 febrile neutropenia. Eleven (13%) of 85 pts had G1 asymptomatic bradycardia considered related to GDC-9545. No pts in either cohort discontinued study treatment due to AEs. PK analysis and clinical data demonstrate no clinically relevant drug-drug interactions between GDC-9545 and palbociclib. Reduced ER, PR, and Ki67 levels, and an ER activity signature, were observed in paired pre- and on-treatment biopsies (n = 12). Eighteen of 33 pts in Cohort A had either confirmed partial responses or were on study 24 weeks (clinical benefit rate 55%). Clinical benefit was observed in pts with prior fulvestrant treatment and with detectable ESR1 mutations at enrollment. Clinical benefit data for both cohorts are anticipated to be mature in April 2020. Conclusions: GDC-9545 was well-tolerated as a single agent and in combination with palbociclib with encouraging PK, PD, and anti-tumor activity in ER+ MBC to support Phase III development. Clinical trial information: NCT03332797 .

Combined PIK3CA and FGFR Inhibition With Alpelisib and Infigratinib in Patients With PIK3CA-Mutant Solid Tumors, With or Without FGFR Alterations

PURPOSE

Concurrent PIK3CA mutations and fibroblast growth factor receptor (FGFR) alterations occur in multiple cancer types, including estrogen receptor-positive breast cancer, bladder cancer, and endometrial cancer. In this first-in-human combination trial, we explored safety and preliminary efficacy of combining the PI3Kα selective inhibitor alpelisib with the FGFR1-4 selective inhibitor infigratinib.

PATIENTS AND METHODS

Patients with PIK3CA-mutant advanced solid tumors, with or without FGFR1-3 alterations, were enrolled in the dose escalation or one of three molecular-defined dose-expansion cohorts. The primary end point was the maximum tolerated dose. Secondary end points included safety, pharmacokinetics, and response. Archival tumor samples were sequenced to explore genomic correlates of response.

RESULTS

In combination, both agents were escalated to full, single-agent recommended doses (alpelisib, 300 mg per day continuously; infigratinib, 125 mg per day 3 weeks on followed by 1 week off). The toxicity profile of the combination was consistent with the established safety profile of each agent, although 71% of all patients required at least one treatment interruption or dose reduction. Molecularly selected dose expansions in breast cancer and other solid tumors harboring PIK3CA mutations, alone or in combination with FGFR alterations, identified sporadic responses, predominately in tumor types and genotypes previously defined to have sensitivity to these agents.

CONCLUSION

The combination of alpelisib and infigratinib can be administered at full single-agent doses, although the high rate of dose interruption or reduction suggests long-term tolerability may be challenging. In exploratory signal-seeking cohorts of patients harboring dual PIK3CA and FGFR1-3 alterations, no clear evidence of synergistic activity was observed.

Molecular markers to predict response to selective fibroblast growth factor receptor inhibitors (FGFRinh) in patients (pts) with FGFR-amplified (amp) or mutated (mut) tumors

2581

Background: Several FGFR and ligand (11q) alterations have been described in cancer. While FGFR fusions are recognized biomarkers of response to FGFRinh, it is still unclear to what extent FGFRamp, FGFR mRNA high expression (mRNAh) or FGFRmut predict sensitivity in the clinic. Methods: Retrospective analysis of pts with molecularly-selected FGFRamp/mRNAh/mut tumors treated with FGFRinh in phase 1 trials at our institution. Mut were detected with IlluminaÒ or Foundation OneÒ. FGFR1-2amp were analyzed by in situ hybridization and mRNA levels by qRT-PCR or nCounterÒ. Clinical benefit (ClinBen) was defined as any tumor shrinkage plus disease control for ³ 4 months (m). Time to progression (TTP) was defined as time between start of FGFRinh and end for any cause. Results: From 2011 to 2016, 36 pts with FGFRamp(25)/mRNAh(5)/mut(6) received an FGFRinh (irreversible- [11 cases (c)] or reversible-FGFR1-4inh [23 c], isoform-specific FGFRinh [3 c] or combo with PI3Kinh [1 c]). Median age 55 yrs (34-76); median prior palliative lines was 3 (0-8); tumor types: breast (17), colorectal (3), esophagus (3), liver (3), lung (3), others (7). Median TTP was 1.67 m (CI 95%; 1.40-2.87). In the FGFRamp/mRNAh population (30), 7 pts achieved ClinBen (23%). 4 out of these seven pts had mRNAh (1 FGFR2amp breast with FGFR2 mRNAh, 1 bladder FGFR3 mRNAh and 2 liver FGFR4 mRNAh without known amp), and 2 pts harboured 11q co-amplification (1 FGFR2amp breast, 1 FGFR2amp head and neck). There was no correlation between ClinBen and level of FGFRamp in the overall population (p = 0.51) or in the breast cancer group (p = 0.29). Of 6 FGFRmut pts, one with bladder cancer had ClinBen (clonal oncogenic FGFR3 S249C). The remaining 5 unresponsive FGFRmut pts had subclonal events, some of these FGFRmut were of unknown functional significance, and had coexisting oncogene mut in MAPK or PI3K pathways. Conclusions: Our results suggest that ClinBen with FGFRinh in the FGFRamp setting is enriched in pts with high mRNA expression and/or ligand co-amplification, and in the FGFRmut population may be dependent on clonality and functionality of the event and co-existence of driver mut.

Evaluation of BGJ398, a Fibroblast Growth Factor Receptor 1-3 Kinase Inhibitor, in Patients With Advanced Solid Tumors Harboring Genetic Alterations in Fibroblast Growth Factor Receptors: Results of a Global Phase I, Dose-Escalation and Dose-Expansion Study

Purpose This two-part, first-in-human study was initiated in patients with advanced solid tumors harboring genetic alterations in fibroblast growth factor receptors (FGFRs) to determine the maximum tolerated dose (MTD), the recommended phase II dose (RP2D), and the schedule, safety, pharmacokinetics, pharmacodynamics, and antitumor activity of oral BGJ398, a selective FGFR1-3 tyrosine kinase inhibitor. Patients and Methods Adult patients were treated with escalating dosages of BGJ398 5 to 150 mg once daily or 50 mg twice daily continuously in 28-day cycles. During expansion at the MTD, patients with FGFR1-amplified squamous cell non-small-cell lung cancer (sqNSCLC; arm 1) or other solid tumors with FGFR genetic alterations (mutations/amplifications/fusions) received BGJ398 daily on a continuous schedule (arm 2), or on a 3-weeks-on/1-week-off schedule (arm 3). Results Data in 132 patients from the escalation and expansion arms are reported (May 15, 2015, cutoff). The MTD, 125 mg daily, was determined on the basis of dose-limiting toxicities in four patients (100 mg, grade 3 aminotransferase elevations [n = 1]; 125 mg, hyperphosphatemia [n = 1]; 150 mg, grade 1 corneal toxicity [n = 1] and grade 3 aminotransferase elevations [n = 1]). Common adverse events in patients treated at the MTD (n = 57) included hyperphosphatemia (82.5%), constipation (50.9%), decreased appetite (45.6%), and stomatitis (45.6%). A similar safety profile was observed using the 3-weeks-on/1-week-off schedule (RP2D). However, adverse event-related dose adjustments/interruptions were less frequent with the 3-weeks-on/1-week-off (50.0%) versus the continuous (73.7%) schedule. Antitumor activity (seven partial responses [six confirmed]) was demonstrated with BGJ398 doses ≥ 100 mg in patients with FGFR1-amplified sqNSCLC and FGFR3-mutant bladder/urothelial cancer. Conclusion BGJ398 at the MTD/RP2D had a tolerable and manageable safety profile and showed antitumor activity in several tumor types, including FGFR1-amplified sqNSCLC and FGFR3-mutant bladder/urothelial cancers.

First Report of a 16SrIII-L Phytoplasma Associated with Frogskin Disease in Cassava (Manihot esculenta Crantz) in Brazil

Cassava (Manihot esculenta Crantz) is a major staple crop in developing countries and a large source of raw material for industrial purposes as flour, starch, and ethanol. In July 2012, 24 cassava genotypes (corresponding to 1.85% of the accessions) with typical symptoms of frogskin disease (CFSD) were observed in one of the maintenance areas of the Brazilian Cassava Germplasm (located at Embrapa Cassava & Fruits, Cruz das Almas, Bahia State, Brazil). All diseased plants were asymptomatic on the aboveground parts (leaves and stem). However, for accessions BGM 880, BGM 1094, BGM 1100, BGM 1212, BGM 1218, and BGM 1526, all roots showed a woody appearance, thickened cork-like peel with opaque aspect, and coalescent lip-like slits in a honeycomb pattern. Based on literature description, two pathogens could be associated with CFSD: a dsRNA virus (belonging to family Reoviridae) and a 16SrIII-L phytoplasma (1). To investigate the presence of phytoplasma associated with the CFSD symptoms, total DNA was extracted from 0.5 g of root tissue collected from both symptomatic and asymptomatic roots by scratching the secondary vessel at the center of the cassava root with a CTAB method. The nested PCR was carried out using phytoplasma-specific primer set P1/Tint followed by R16F2n/R16R2, targeting the 16S rRNA gene sequence of 1.2 kb in length, for the final reaction (4). No phytoplasma was detected in asymptomatic cassava roots that were sampled from the same field. A posterior extraction of total RNA was made but no dsRNA was noticed on the agarose gel, and reaction of RT-PCR with specific primers (2) had no amplification. In order to characterize the strains, the 1.2-kb amplicon was digested with BamHI, MseI, MspI, KpnI, and TaqI endonucleases. The resulting patterns indicated that the symptomatic accessions were infected with a phytoplasma belonging to the 16SrIII group, sharing similarities with pseudo gel mapping from the reference strain of Peach X-Disease Phytoplasma (GenBank Accession No. L33733). Nested PCR products from accessions BGM 1526 and BGM 1212 were purified and sequenced by Macrogen, (Seoul, South Korea) in both directions, manually edited, and the consensus sequences were deposited in the NCBI database (GenBank Accession Nos. KF019184 and KF019185). Phylogenetic studies were conducted based on maximum parsimony, neighbor-joining, and maximum likelihood analysis for 16S rRNA. The phytoplasma 16S rRNA gene sequences from both strains had 99% identity (P < 0.0001) with the 16SrIII-L CFSD phytoplasma (EU346761 and AY737647), described by Alvarez et al. (1) infecting cassava in Colombia. To our knowledge, this is the first report of a phytoplasma associated with Cassava Frogskin Disease in Brazil, where only the dsRNA virus was recognized as causing this symptom (3). This is not likely to be an isolated case, and possibly more cassava plants are infected with this phytoplasma in Brazil. Due to the difficulties to observe the symptoms at the field level, this could be an emerging disease in that country. References: (1) E. Alvarez et al. Plant. Dis. 93:1139, 2009. (2) L. A. Calvert et al. J. Phytopathol. 156:647, 2008. (3) L. S. Poltroniere et al. Comun. Tec., Belem-PA. 006:2p, 1999. (4) C. D. Smart et al. Appl. Environ. Microb. 62:2988, 1996.