Abstract 2677: JZP815, a potent and selective pan-RAF inhibitor, demonstrates efficacy in RAF and RAS mutant tumor pre-clinical models

Activation of the mitogen-activated protein kinase (MAPK) pathway by oncogenic mutations in RAS and RAF is a frequent driver of human cancer. Targeting specific components of the pathway is a precise and rational route to deliver benefits to cancer patients with high unmet therapeutic needs. The RAF kinase proteins (ARAF, BRAF, CRAF) are core pathway components which mediate MAPK signaling. Mutations in these critical signaling proteins leads to constitutive activation of the MAPK pathway and tumor growth. Using state of the art screening methodologies and medicinal chemistry we discovered and developed a next generation pan-RAF kinase inhibitor, JZP815, which potently inhibits wild-type and mutant RAF kinases in cell-free and cell-based assays. JZP815 is a selective RAF kinase inhibitor that suppresses all 3 RAF kinase family members at low-to-sub nanomolar potencies in cell-free assays. Moreover, in tumor cells JZP815 does not induce significant paradoxical pathway activation, observed with approved 1st generation BRAF-selective inhibitors, while demonstrating equivalent potencies for MAPK pathway inhibition driven by either mutant RAF monomers or RAS-induced RAF dimers in tumor cells. JZP815 significantly inhibited tumor growth as a single agent in multiple mouse xenograft solid tumor models harboring RAS and/or BRAF mutations. Furthermore, JZP815’s favorable pharmacokinetic profile sustained on-target pathway pharmacodynamic responses in a predictable dose and time dependent manner. JZP815 demonstrated enhanced activity when combined with inhibitors of other MAPK pathway components in both class 2 and class 3 mutant BRAF patient-derived tumor cells ex vivo, and KRAS mutant NSCLC and CRC xenografts in vivo. In summary, JZP815 is a potent and selective pan-RAF inhibitor that is orally bioavailable in multiple preclinical species with a well-behaved safety profile and pharmacokinetic properties predicted to provide drug exposure required for target engagement in humans, and therefore suitable for advancing into first-in-human trials.

Citation Format: Robert Hauptschein, Simon Woodcock, Andrew Belfield, Helen Mason, Dorottya Keppel, Svetlana Markova, Kyuri Kim, Shane Roller, Caroline Phillips, Clifford D. Jones, Robin C. Humphreys. JZP815, a potent and selective pan-RAF inhibitor, demonstrates efficacy in RAF and RAS mutant tumor pre-clinical models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2677.

Abstract A199: Development of a series of novel, potent and selective inhibitors of cFMS as a potential treatment for CSF1 expressing cancers via the modulation of the tumor microenvironment and the repolarization of macrophages

Redx Oncology has developed novel small molecule inhibitors of Colony Stimulating Factor 1 Receptor (CSF1R or cFMS) which have proven to be efficacious in an in vivo bone erosion model.

cFMS is a key receptor involved in the survival, modulation and maintenance of cells of the monocyte- macrophage lineage (which include osteoclasts in the bone). In bone, osteoclasts express cFMS whilst osteoblasts express CSF1. The CSF1/cFMS axis is involved, along with RANKL, in the dynamics of bone metabolism. Metastatic tumor cells that express cFMS can be recruited into the bone as part of this dynamic metabolism. Moreover, recent literature has shown that cFMS inhibitors are able to ‘re-educate’ pro-tumurogenic M2 macrophages, which are present in the tumor microenvironment in a CSF positive tumor, into the anti-tumurogenic M1 phenotype.

We present here results of the lead optimization of our novel cFMS inhibitor series.

REDX05182 is a lead compound from the series and is a highly selective cFMS inhibitor which shows potent inhibition of cFMS. It also inhibits the related kinases cKIT, PDGFRA and PDGFRB. Interestingly, however, it exhibits good selectivity over related kinases Flt3 and KDR (VEGFR2). It displays low nanomolar binding affinity for cFMS in a biochemical assay (6nM (5 hours)) and displays slow binding kinetics.

In cellular assays, REDX05182 shows nanomolar inhibition of CSF1 driven cell proliferation of the M-NFS-60 cell line (126nM), CSF1 stimulated phosphorylation of CSF1R in THP-1 cells (182nM) and CSF-1 stimulated differentiation of rat primary macrophages into osteoclasts (102nM).

REDX05182 demonstrates good exposure and bioavailability in vivo and has shown efficacy in a rat model of cancer induced bone resorption using MRMT-1 cancer cells. At 30mg/kg BID a statistically significant improvement in the allodynia score is observed. Also at this dose the osteoclast count in the bone is returned to that of normal bone and the osteolysis is reduced.

Interestingly, REDX05182 has also demonstrated the re-polarization of macrophages from the pro-tumurogenic M2 phenotype to the anti-tumurogenic M1 phenotype in human pBMC's.

In summary, REDX05182 is a potent cFMS inhibitor which has shown activity in vivo and in vitro. Work is continuing on the project to further optimize this lead compound to deliver a clinical candidate.

Citation Format: Sachin G. Mahale, Andrew Belfield, Jamie Wright, Mary-Ann Campbell, Matilda Bingham, Richard Armer. Development of a series of novel, potent and selective inhibitors of cFMS as a potential treatment for CSF1 expressing cancers via the modulation of the tumor microenvironment and the repolarization of macrophages. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2015 Nov 5-9; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2015;14(12 Suppl 2):Abstract nr A199.

Drug targeting to monocytes and macrophages using esterase-sensitive chemical motifs

The therapeutic and toxic effects of drugs are often generated through effects on distinct cell types in the body. Selective delivery of drugs to specific cells or cell lineages would, therefore, have major advantages, in particular, the potential to significantly improve the therapeutic window of an agent. Cells of the monocyte-macrophage lineage represent an important target for many therapeutic agents because of their central involvement in a wide range of diseases including inflammation, cancer, atherosclerosis, and diabetes. We have developed a versatile chemistry platform that is designed to enhance the potency and delivery of small-molecule drugs to intracellular molecular targets. One facet of the technology involves the selective delivery of drugs to cells of the monocyte-macrophage lineage, using the intracellular carboxylesterase, human carboxylesterase-1 (hCE-1), which is expressed predominantly in these cells. Here, we demonstrate selective delivery of many types of intracellularly targeted small molecules to monocytes and macrophages by attaching a small esterase-sensitive chemical motif (ESM) that is selectively hydrolyzed within these cells to a charged, pharmacologically active drug. ESM versions of histone deacetylase (HDAC) inhibitors, for example, are extremely potent anticytokine and antiarthritic agents with a wider therapeutic window than conventional HDAC inhibitors. In human blood, effects on monocytes (hCE-1-positive) are seen at concentrations 1000-fold lower than those that affect other cell types (hCE-1-negative). Chemical conjugates of this type, by limiting effects on other cells, could find widespread applicability in the treatment of human diseases where monocyte-macrophages play a key role in disease pathology.

Discovery of 2-(6-{[(6-fluoroquinolin-2-yl)methyl]amino}bicyclo[3.1.0]hex-3-yl)-N-hydroxypyrimidine-5-carboxamide (CHR-3996), a class I selective orally active histone deacetylase inhibitor

A novel series of HDAC inhibitors demonstrating class I subtype selectivity and good oral bioavailability is described. The compounds are potent enzyme inhibitors (IC₅₀ values less than 100 nM), and improved activity in cell proliferation assays was achieved by modulation of polar surface area (PSA) through the introduction of novel linking groups. Employing oral pharmacokinetic studies in mice, comparing drug levels in spleen to plasma, we selected compounds that were tested for efficacy in human tumor xenograft studies based on their potential to distribute into tumor. One compound, 21r (CHR-3996), showed good oral activity in these models, including dose-related activity in a LoVo xenograft. In addition 21r showed good activity in combination with other anticancer agents in in vitro studies. On the basis of these results, 21r was nominated for clinical development.

Onco-developmental protein concentrations in the sera of patients with ovarian cancer prior to treatment

Eight onco-developmental proteins have been measured in the serum of women prior to their operation and treatment for ovarian cancer. Alpha-foetoprotein, CEA, hCG and PAPP-A were not often elevated whereas CPAP, SP1, CanAg 50 and CA 125 were. Many of our findings differed from those of previous workers, possibly due to differences in clinical material and analytical technique. We conclude that large profiles of tumour markers are no longer of use in the investigation of ovarian cancer. At the present time we think that CA 125 could prove the most useful marker in the investigation of ovarian cancer.

Preliminary observations on the application of carcino-placental alkaline phosphatase to the investigation of patients with seminoma of the testes

Suitable tumour markers for monitoring the treatment of seminoma of the testis have not yet been established in clinical practice. Carcino-placental alkaline phosphatase (CPAP) has been suggested for this purpose but it is difficult to detect and specifically analyse this enzyme. We have devised an immunoenzymatic method of analysis in which cross-reactions with liver type and intestinal alkaline phosphatase are minimal and we have applied this test to seven patients with histologically proven seminoma. CPAP was raised in 4 patients prior to treatment and chorionic gonadotrophin in two of these. Alpha-fetoprotein was normal in all cases. We conclude that the use of CPAP in monitoring treatment of testicular seminoma is worthy of further attention.

Lack of comparability between CEA analyses using three different methods

Three different methods for the assay of carcinoembryonic antigen were investigated--radioimmunoassay, enzyme-linked immunoassay, and a commercial immunoradiometric assay. Two standard preparations of CEA were used: the 1st British Standard (73/601) and a commercial preparation obtained as a component of the IRMA kit. Serum samples were assayed by each method against each standard material. Significant differences between results were obtained when the different methods were compared. When using the two standards in the same assay system no significant differences were found between results. A possible explanation and the implications of these findings for the routine assay of CEA are discussed.

Obstetric aspects of the use in pregnancy-associated hypertension of the beta-adrenoceptor antagonist atenolol

The obstetric implications of the use of the beta-adrenoceptor antagonist atenolol have been evaluated in a prospective, randomized, double-blind, and placebo-controlled study involving 120 women with pregnancy-associated hypertension. The clinical interpretation of antenatal and intrapartum cardiotocographs was uninfluenced by atenolol. Human placental lactogen concentration fell in the atenolol group, but this was not an indicator of subsequent fetal distress. Other obstetric indices, such as urinary estriol excretion, were the same in both groups. Spontaneous premature labor occurred in five women receiving placebo but in none who received atenolol. Together with previously reported findings on pregnancy outcome, our study leads us to conclude that beta-blockers such as atenolol can appropriately be used in the management of hypertension during pregnancy.

The predictive value of three pregnancy-associated proteins in the detection of the light-for-dates baby

Three pregnancy-associated proteins, human placental lactogen, pregnancy-specific beta 1-glycoprotein and pregnancy-associated plasma protein-A have been measured in two groups of pregnant women. One group subsequently gave birth to children of normal birthweight, the other group were all delivered of a child with a birthweight less than the 10th centile. From the results obtained the values of the tests in predicting intrauterine growth retardation have been calculated. Human placental lactogen proved to be the most useful of the tests compared in predicting intrauterine growth retardation in the individual patient.

The effect of excess antigen on the enzyme-linked immunosorbent assay of onco-placental proteins

The time course of the antigen-antibody reaction between human chorionic gonadotrophin, pregnancy specific beta 1 glycoprotein and pregnancy associated plasma protein A and their respective immobilised antibodies has been investigated. All 3 antigens showed enhanced binding with increasing length of incubation up to a maximum value, followed by a decrease. It is suggested that the diminution in binding at high antigen concentration is caused by the solubilisation of the immobilised antigen-antibody complex and that this is promoted by the high concentration of antigen.

An ELISA for pregnancy-associated plasma protein A

An enzyme-linked immunoassay for pregnancy-associated plasma protein A is described. The assay is sensitive (7.6 IU/l) and precise (overall CV varied between 8.9% and 10.8%). Recovery was 100% over the working range. Parallel behaviour was observed between the International Reference Preparation 78/610 and pregnancy serum, thus allowing calibration of a laboratory standard pool against IRP 78/610.

Human placental lactogen and pregnancy-specific beta 1-glycoprotein in pregnant diabetic women

Serum placental lactogen (hPL) and pregnancy-specific beta 1-glycoprotein (SP1) concentrations were measured in 16 insulin-dependent pregnant diabetic women and in 16 non-diabetic control subjects matched for placental weight. hPL concentrations were found to be significantly higher in diabetics with placental weight greater than 90th centile compared with those in (i) non-diabetic controls with placental weight greater than 90th centile and (ii) diabetics with placental weights less than 90th centile. SP1 concentrations were higher in both diabetic groups compared with those in their respective non-diabetic controls, but no difference existed between the two diabetic groups. In the control subjects infant birthweights were lower in the women with small placentae, but no such difference was observed between the two diabetic groups.

Kernicterus at low levels of serum bilirubin: the impact of bilirubin albumin-binding capacity. A 10-year retrospective survey

A retrospective survey of neonatal post-mortems over a 10-year period was made to establish the incidence of kernicterus and the associated laboratory abnormalities. Cases with evidence of kernicterus without hyperbilirubinaemia were found to have significantly lower reserve albumin-binding capacity (RABC) than the control group. The results suggest that RABC estimation is a necessary adjunct in the assessment of the jaundiced, low birthweight neonate.

Pregnancy specific beta 1 glycoprotein: a comparison of analysis by radioimmunoassay and enzyme linked immunosorbent assay observations on patients with malignant teratoma of testis

A comparison of serum pregnancy specific beta 1 glycoprotein analysis by enzyme linked immunosorbent assay and radioimmunoassay has been made. Excellent correlation was obtained between the two methods but radioimmunoassay was found to be more precise and to have a lower detection limit than enzyme linked immunosorbent assay. Using the more sensitive radioimmunoassay system, 2 out of 10 control male sera were found to contain detectable levels of pregnancy specific beta 1 glycoprotein. Sequential results are presented on patients with diagnosed malignant teratoma of testis who were undergoing chemotherapy.

Enzyme-linked immunoassay for placental lactogen in human serum

We describe an enzyme-linked immunoassay for measuring human placental lactogen (HPL) in serum. After suitable dilution, sera are pipetted into the wells of polyvinyl microtitre plates previously coated with anti-HPL. After incubation the sera are decanted, and replaced by a conjugate of horseradish peroxidase and anti-HPL. An amount of enzyme proportional to the concentration of HPL in the serum is bound to the wells via an antibody—HPL—antibody bridge. Peroxidase activity is measured by oxidation of o-phenylenediamine, the resulting color being related to the concentration of HPL. Results correlate well with those by radioimmunoassay (r = 0.96). Our between-assay coefficient of variation was 13%; no discernible effect of protein was observed. This 4-h assay can be used to monitor placental function in pregnancy.

Enzyme-linked immunoassay for placental lactogen in human serum

We describe an enzyme-linked immunoassay for measuring human placental lactogen (HPL) in serum. After suitable dilution, sera are pipetted into the wells of polyvinyl microtitre plates previously coated with anti-HPL. After incubation the sera are decanted, and replaced by a conjugate of horseradish peroxidase and anti-HPL. An amount of enzyme proportional to the concentration of HPL in the serum is bound to the wells via an antibody--HPL--antibody bridge. Peroxidase activity is measured by oxidation of o-phenylenediamine, the resulting color being related to the concentration of HPL. Results correlate well with those by radioimmunoassay (r = 0.96). Our between-assay coefficient of variation was 13%; no discernible effect of protein was observed. This 4-h assay can be used to monitor placental function in pregnancy.

The quantitation of pregnancy specific beta 1-glycoprotein by enzyme linked immunoassay

A rapid enzyme linked immunoassay for pregnancy specific beta 1-glycoprotein is described. The method is sensitive and precise (within batch C.V. = 6.5-7.4%) and should be suitable for the biochemical monitoring of pregnancy and the investigation of patients suffering from various malignancies.

Serum enzymes in colorectal cancer

A study of the value of serum enzymes in 184 patients with colorectal cancer has been performed. The enzymes studied were gamma glutamyltransferase (gammaGT), alkaline phosphatase (AP), lactate dehydrogenase (LDH), 5'-nucleotidase (5'-NT), glutathione reductase (GR), alanine and aspartate transaminases. In patients without liver metastases, elevated enzyme levels were found in 11-55% preoperatively. 5'-NT showed the least number of elevated activities, while gammaGT activities were increased in 29% and LDH in 55%. The percentage of elevated enzyme levels rose significantly in the early postoperative period. Patients with liver metastases showed increased enzyme activities in 40-60% preoperatively: gammaGT was the most sensitive indicator. Increased enzyme activity was related to the degree of liver involvement with secondary tumor. With extensive liver metastases, gammaGT levels were increased in 82%. It is concluded that serum enzymes are of limited value in the preoperative detection of liver metastases, and particularly when tumor involvement of the liver is small.

Enzyme multiplied immunoassay of phenobarbital by LKB reaction Rate Analyser: a comparison with analysis by gas-liquid chromatography

A procedure for the enzyme multiplied immunoassay of phenobarbital using the LKB Reaction Rate Analyser is described. The temperature optimum, linearity, specificity, and precision of the assay are reported. A highly significant correlation coefficient is obtained when the technique is compared with gas-liquid chromatography by analysing human sera containing a range of phenobarbital levels.

Normal ranges and diagnostic value of serum 5'nucleotidase and alkaline phosphatase activities in infancy

Determinations of serum alkaline phosphatase (APase) and 5′nucleotidase (5Nase) activities have been carried out in 159 children investigated for possible disease of liver or bones, and in 147 children in whom these possibilities never arose. The latter group, which served as a control population, showed 5Nase levels very much lower than those encountered in a normal adult population. APase values in this group rose after birth, fell after the first year, and remained stable until puberty when the range increased slightly. APase was raised in 73% of children with hepatobiliary disease, 65% of children with bone disease, and 28% of children in whom there was no evidence of disease of either type. The corresponding figures for 5Nase activity were 87%, 6%, and 3%, and the degree of increase encountered in hepatobiliary disease was proportionately higher than the increase of APase seen in the same subjects. It is concluded that 5Nase is superior to APase in the diagnosis of hepatobiliary disease in infancy.

Colorimetric determination of serum acid phosphatase activity using adenosine 3'-monophosphate as substrate

The hydrolysis of adenosine 3'-monophosphate by serum acid phosphatase has been coupled to the liberation of ammonia from the adenosine generated through the action of exogenous adenosine deaminase. The ammonia is measured at the end of the incubation by a modification of the phenol-hypochlorite reaction of Berthelot. Optimum conditions for the enzyme reaction have been defined. Inhibition of the Berthelot reaction by the serum used in the assay is small, and may be compensated by a correction factor. Although the value for the control is high in relation to the test over the normal range, this is largely outweighed by the good sensitivity and precision of the method. The substrate is not significantly hydrolysed by erythrocyte acid phosphatase within the limits encountered in haemolysed sera. Experience of the method in routine hospital diagnosis compared favorably with that of a standard method employing disodium phenyl phosphate as substrate. It is suggested that activities greater than 3.1 IU/l should be further investigated and those greater than 3.7 IU/l should be regarded as definitely raised. The stability of human serum AcPase when promptly separated and held at 4 degrees C or - 20 degrees C was confirmed. At room temperature, acidification to pH 6.0 greatly improved stability.

Activation of serum 5' nucleotidase by magnesium ions and its diagnostic applications

Magnesium ions increase the hydrolysis of adenosine 5' monophosphate (5' AMP) by human serum at pH 7.9 but not at pH 9.3. The additional hydrolysis at pH 7.9 is predominantly due to increased activity of the specific phosphatase 5' nucleotidase (5Nase). This increase is proportional to enzyme concentration and has been employed as a measure of 5Nase activity in a sensitive micro-estimation. The normal range for serum 5Nase activity by this technique was 0 to 20 mIU/ml. In a series of over 200 patients, raised values were found frequently in hepatobiliary disease and infrequently in bone disease. Assay of 5Nase activity gave a more reliable indication of the source of raised serum alkaline phosphatase than isoenzyme electrophoresis in agar gel. The correlation between activities of the two enzymes was low in bone disease generally, and fairly good in hepatobiliary disease. The closest correlation was found in patients with parenchymal liver disease.