Two Phase 3 Trials of Gantenerumab in Early Alzheimer's Disease

BACKGROUND

Monoclonal antibodies that target amyloid-beta (Aβ) have the potential to slow cognitive and functional decline in persons with early Alzheimer's disease. Gantenerumab is a subcutaneously administered, fully human, anti-Aβ IgG1 monoclonal antibody with highest affinity for aggregated Aβ that has been tested for the treatment of Alzheimer's disease.

METHODS

We conducted two phase 3 trials (GRADUATE I and II) involving participants 50 to 90 years of age with mild cognitive impairment or mild dementia due to Alzheimer's disease and evidence of amyloid plaques on positron-emission tomography (PET) or cerebrospinal fluid (CSF) testing. Participants were randomly assigned to receive gantenerumab or placebo every 2 weeks. The primary outcome was the change from baseline in the score on the Clinical Dementia Rating scale-Sum of Boxes (CDR-SB; range, 0 to 18, with higher scores indicating greater cognitive impairment) at week 116.

RESULTS

A total of 985 and 980 participants were enrolled in the GRADUATE I and II trials, respectively. The baseline CDR-SB score was 3.7 in the GRADUATE I trial and 3.6 in the GRADUATE II trial. The change from baseline in the CDR-SB score at week 116 was 3.35 with gantenerumab and 3.65 with placebo in the GRADUATE I trial (difference, -0.31; 95% confidence interval [CI], -0.66 to 0.05; P = 0.10) and was 2.82 with gantenerumab and 3.01 with placebo in the GRADUATE II trial (difference, -0.19; 95% CI, -0.55 to 0.17; P = 0.30). At week 116, the difference in the amyloid level on PET between the gantenerumab group and the placebo group was -66.44 and -56.46 centiloids in the GRADUATE I and II trials, respectively, and amyloid-negative status was attained in 28.0% and 26.8% of the participants receiving gantenerumab in the two trials. Across both trials, participants receiving gantenerumab had lower CSF levels of phosphorylated tau 181 and higher levels of Aβ42 than those receiving placebo; the accumulation of aggregated tau on PET was similar in the two groups. Amyloid-related imaging abnormalities with edema (ARIA-E) occurred in 24.9% of the participants receiving gantenerumab, and symptomatic ARIA-E occurred in 5.0%.

CONCLUSIONS

Among persons with early Alzheimer's disease, the use of gantenerumab led to a lower amyloid plaque burden than placebo at 116 weeks but was not associated with slower clinical decline. (Funded by F. Hoffmann-La Roche; GRADUATE I and II ClinicalTrials.gov numbers, NCT03444870 and NCT03443973, respectively.).

Transforming activities of the NUP98-KMT2A fusion gene associated with myelodysplasia and acute myeloid leukemia

Inv(11)(p15q23), found in myelodysplastic syndromes and acute myeloid leukemia, leads to expression of a fusion protein consisting of the N-terminal of nucleoporin 98 (NUP98) and the majority of the lysine methyltransferase 2A (KMT2A). To explore the transforming potential of this fusion we established inducible iNUP98-KMT2A transgenic mice. After a median latency of 80 weeks, over 90% of these mice developed signs of disease, with anemia and reduced bone marrow cellularity, increased white blood cell numbers, extramedullary hematopoiesis, and multilineage dysplasia. Additionally, induction of iNUP98-KMT2A led to elevated lineage marker-negative Sca-1⁺ c-Kit⁺ cell numbers in the bone marrow, which outcompeted wildtype cells in repopulation assays. Six iNUP98-KMT2A mice developed transplantable acute myeloid leukemia with leukemic blasts infiltrating multiple organs. Notably, as reported for patients, iNUP98-KMT2A leukemic blasts did not express increased levels of the HoxA-B-C gene cluster, and in contrast to KMT2A-AF9 leukemic cells, the cells were resistant to pharmacological targeting of menin and BET family proteins by MI-2-2 or JQ1, respectively. Expression of iNUP98-KMT2A in mouse embryonic fibroblasts led to an accumulation of cells in G1 phase, and abrogated replicative senescence. In bone marrow-derived hematopoietic progenitors, iNUP98-KMT2A expression similarly resulted in increased cell numbers in the G1 phase of the cell cycle, with aberrant gene expression of Sirt1, Tert, Rbl2, Twist1, Vim, and Prkcd, mimicking that seen in mouse embryonic fibroblasts. In summary, we demonstrate that iNUP98-KMT2A has in vivo transforming activity and interferes with cell cycle progression rather than primarily blocking differentiation.

Abstract 1892: Discovery of targeted therapies for acute myeloid leukemia patients with NUP98-NSD1 and FLT3-ITD

NUP98-NSD1 fusion resulting from the t(5;11)(q35;p15.5) is a clinically significant indicator of adverse prognosis in AML. While the understanding of NUP98-NSD1-driven leukaemogenesis has increased over the years, these patients still suffer from highly progressive disease with no effective therapies. To address this challenge, we analyzed primary patient samples and experimental cell models by high-throughput drug screening and RNA sequencing.

Primary samples included bone marrow mononuclear cells (BM MNCs) from three NUP98-NSD1/FLT3-ITD AML patients and ten healthy donors. Experimental cells included lineage-depleted balb/c BM cells transduced with chimeric NUP98-NSD1 and FLT3-ITD retroviruses alone or together, and Ba/F3 cells transduced with human-cloned NUP98-NSD1 lentivirus. The cells were seeded on 384-well plates containing up to 306 approved and investigational drugs in five concentrations over a 10,000-fold range and incubated for 72h at +37°C. Cell viabilities were measured using CellTiter-Glo®. Drug sensitivity scores (DSS) were calculated from area under the dose response curve and select DSS by subtracting DSS of mock-transduced parental cells from the experimental model.

We discovered 14 drugs with highly significant mean DSS difference (p < 0.001) between patients and healthy controls. Further analysis revealed that only two of these drugs (dasatinib and navitoclax) had positive correlation between DSS and BM blast percentage (Pearson's R: 0.83-0.98) as well as higher mean DSS in the context of other AML patients with (n = 9) and without (n = 38) FLT3-ITD. Experimental balb/c cells expressing NUP98-NSD1 had significantly increased sensitivity to BCL2 inhibitors (n = 3) (p < 0.05), while cells co-expressing NUP98-NSD1 and FLT3-ITD had significantly increased sensitivity to FLT3 (n = 11) and MEK inhibitors (n = 6) in comparison to cells expressing FLT3-ITD alone. In pilot combination screen, select efficacy of FLT3 and MEK inhibitors was further increased in the dual positive cells by dasatinib (100 nM). In synergy screens, navitoclax-dasatinib and navitoclax-quizartinib combinations were highly synergistic in primary cells and balb/c cells co-expressing NUP98-NSD1 and FLT3-ITD. Gene expression analysis showed significant up-regulation of dasatinib target genes LCK and FGR, and navitoclax target gene BCL2A1 in the primary AML cells. Interestingly, BCL2A1 was also upregulated in the balb/c BM cells expressing NUP98-NSD1 alone or with FLT3-ITD, but not in cells expressing FLT3-ITD alone.

Taken together, we have identified potential candidate drugs and drug combinations for t(5;11) positive AML. Although the sample size was small, our data suggests that further research into BCL2 inhibitors in combination with TKIs may eventually translate to better survival outlook of AML patients with t(5;11).

Citation Format: Jarno Kivioja, Angeliki Thanasopoulou, Mika Kontro, Ashwini Kumar, Bhagwan Yadav, Muntasir Mamun Majumder, Kimmo Porkka, Juerg Schwaller, Caroline A. Heckman. Discovery of targeted therapies for acute myeloid leukemia patients with NUP98-NSD1 and FLT3-ITD [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 1892.

Generation of a Selective Small Molecule Inhibitor of the CBP/p300 Bromodomain for Leukemia Therapy

The histone acetyltransferases CBP/p300 are involved in recurrent leukemia-associated chromosomal translocations and are key regulators of cell growth. Therefore, efforts to generate inhibitors of CBP/p300 are of clinical value. We developed a specific and potent acetyl-lysine competitive protein-protein interaction inhibitor, I-CBP112, that targets the CBP/p300 bromodomains. Exposure of human and mouse leukemic cell lines to I-CBP112 resulted in substantially impaired colony formation and induced cellular differentiation without significant cytotoxicity. I-CBP112 significantly reduced the leukemia-initiating potential of MLL-AF9(+) acute myeloid leukemia cells in a dose-dependent manner in vitro and in vivo. Interestingly, I-CBP112 increased the cytotoxic activity of BET bromodomain inhibitor JQ1 as well as doxorubicin. Collectively, we report the development and preclinical evaluation of a novel, potent inhibitor targeting CBP/p300 bromodomains that impairs aberrant self-renewal of leukemic cells. The synergistic effects of I-CBP112 and current standard therapy (doxorubicin) as well as emerging treatment strategies (BET inhibition) provide new opportunities for combinatorial treatment of leukemia and potentially other cancers.

Potent co-operation between the NUP98-NSD1 fusion and the FLT3-ITD mutation in acute myeloid leukemia induction

The NUP98-NSD1 fusion, product of the t(5;11)(q35;p15.5) chromosomal translocation, is one of the most prevalent genetic alterations in cytogenetically normal pediatric acute myeloid leukemias and is associated with poor prognosis. Co-existence of an FLT3-ITD activating mutation has been found in more than 70% of NUP98-NSD1-positive patients. To address functional synergism, we determined the transforming potential of retrovirally expressed NUP98-NSD1 and FLT3-ITD in the mouse. Expression of NUP98-NSD1 provided mouse strain-dependent, aberrant self-renewal potential to bone marrow progenitor cells. Co-expression of FLT3-ITD increased proliferation and maintained self-renewal in vitro. Transplantation of immortalized progenitors co-expressing NUP98-NSD1 and FLT3-ITD into mice resulted in acute myeloid leukemia after a short latency. In contrast, neither NUP98-NSD1 nor FLT3-ITD single transduced cells were able to initiate leukemia. Interestingly, as reported for patients carrying NUP98-NSD1, an increased Flt3-ITD to wild-type Flt3 mRNA expression ratio with increased FLT3-signaling was associated with rapidly induced disease. In contrast, there was no difference in the expression levels of the NUP98-NSD1 fusion or its proposed targets HoxA5, HoxA7, HoxA9 or HoxA10 between animals with different latencies to develop disease. Finally, leukemic cells co-expressing NUP98-NSD1 and FLT3-ITD were very sensitive to a small molecule FLT3 inhibitor, which underlines the significance of aberrant FLT3 signaling for NUP98-NSD1-positive leukemias and suggests new therapeutic approaches that could potentially improve patient outcome.

PFI-1, a highly selective protein interaction inhibitor, targeting BET Bromodomains

Bromo and extra terminal (BET) proteins (BRD2, BRD3, BRD4, and BRDT) are transcriptional regulators required for efficient expression of several growth promoting and antiapoptotic genes as well as for cell-cycle progression. BET proteins are recruited on transcriptionally active chromatin via their two N-terminal bromodomains (BRD), a protein interaction module that specifically recognizes acetylated lysine residues in histones H3 and H4. Inhibition of the BET-histone interaction results in transcriptional downregulation of a number of oncogenes, providing a novel pharmacologic strategy for the treatment of cancer. Here, we present a potent and highly selective dihydroquinazoline-2-one inhibitor, PFI-1, which efficiently blocks the interaction of BET BRDs with acetylated histone tails. Cocrystal structures showed that PFI-1 acts as an acetyl-lysine (Kac) mimetic inhibitor efficiently occupying the Kac binding site in BRD4 and BRD2. PFI-1 has antiproliferative effects on leukemic cell lines and efficiently abrogates their clonogenic growth. Exposure of sensitive cell lines with PFI-1 results in G1 cell-cycle arrest, downregulation of MYC expression, as well as induction of apoptosis and induces differentiation of primary leukemic blasts. Intriguingly, cells exposed to PFI-1 showed significant downregulation of Aurora B kinase, thus attenuating phosphorylation of the Aurora substrate H3S10, providing an alternative strategy for the specific inhibition of this well-established oncology target.

Silencing of CCDC6 reduces the expression of 14-3-3σ in colorectal carcinoma cells

Coiled-coil domain containing 6 (CCDC6) is frequently rearranged in papillary thyroid carcinomas participating in the formation of RET/PTC1 oncogene. Other rearrangements involving CCDC6 have also been identified demonstrating its high susceptibility to chromosomal recombination. Malignancies bearing CCDC6 fusion genes are developed in a background where CCDC6 is either lost or deregulated. Our aim was to identify interacting proteins which are affected by the silencing of CCDC6 expression and could possibly link CCDC6 deregulation to cancer causality. Therefore, a proteomic approach was adopted using a human cancer cell-line (HCT116) where CCDC6 expression was silenced by lentiviral shRNA constructs. 14-3-3σ down-regulation in the absence of CCDC6 was revealed and verified by western blot analysis and confocal microscopy. Only the levels and not the topology of CCDC6 were altered. The down-regulation of 14-3-3σ in the absence of CCDC6 demonstrated their direct association and supports the notion that CCDC6 contributes to cancer development, possibly through malignant pathways involving 14-3-3σ.

Loss of CCDC6 affects cell cycle through impaired intra-S-phase checkpoint control

In most cancers harboring Ccdc6 gene rearrangements, like papillary thyroid tumors or myeloproliferative disorders, the product of the normal allele is supposed to be functionally impaired or absent. To address the consequence of the loss of CCDC6 expression, we applied lentiviral shRNA in several cell lines. Loss of CCDC6 resulted in increased cell death with clear shortening of the S phase transition of the cell cycle. Upon exposure to etoposide, the cells lacking CCDC6 did not achieve S-phase accumulation. In the absence of CCDC6 and in the presence of genotoxic stress, like etoposide treatment or UV irradiation, increased accumulation of DNA damage was observed, as indicated by a significant increase of pH2Ax Ser139. 14-3-3σ, a major cell cycle regulator, was down-regulated in CCDC6 lacking cells, regardless of genotoxic stress. Interestingly, in the absence of CCDC6, the well-known genotoxic stress-induced cytoplasmic sequestration of the S-phase checkpoint CDC25C phosphatase did not occur. These observations suggest that CCDC6 plays a key role in cell cycle control, maintenance of genomic stability and cell survival and provide a rational of how disruption of CCDC6 normal function contributes to malignancy.

Gelsolin expression is necessary for the development of modelled pulmonary inflammation and fibrosis

BACKGROUND

Despite intense research efforts, the aetiology and pathogenesis of idiopathic pulmonary fibrosis remain poorly understood. Gelsolin, an actin-binding protein that modulates cytoskeletal dynamics, was recently highlighted as a likely disease modifier through comparative expression profiling and target prioritisation.

METHODS

To decipher the possible role of gelsolin in pulmonary inflammation and fibrosis, immunocytochemistry on tissue microarrays of human patient samples was performed followed by computerised image analysis. The results were validated in the bleomycin-induced animal model of pulmonary inflammation and fibrosis using genetically-modified mice lacking gelsolin expression. Moreover, to gain mechanistic insights into the mode of gelsolin activity, a series of biochemical analyses was performed ex vivo in mouse embryonic fibroblasts.

RESULTS

Increased gelsolin expression was detected in lung samples of patients with idiopathic interstitial pneumonia as well as in modelled pulmonary inflammation and fibrosis. Genetic ablation of gelsolin protected mice from the development of modelled pulmonary inflammation and fibrosis attributed to attenuated epithelial apoptosis.

CONCLUSIONS

Gelsolin expression is necessary for the development of modelled pulmonary inflammation and fibrosis, while the caspase-3-mediated gelsolin fragmentation was shown to be an apoptotic effector mechanism in disease pathogenesis and a marker of lung injury.