Real world data on outcomes of anti-CD38 antibody treated, including triple class refractory, patients with multiple myeloma: a multi-institutional report from the Canadian Myeloma Research Group (CMRG) Database

Multiple myeloma (MM) remains incurable despite the availability of novel agents. This multi-center retrospective cohort study used the Canadian Myeloma Research Group Database to describe real-world outcomes of patients withanti-CD38 monoclonal antibody (mAb) refractory MM subsequently treated with standard of care (SoC) regimens. Patients with triple class refractory (TCR) disease (refractory to a proteasome inhibitor, immunomodulatory drug, and anti-CD38 mAb) were examined as a distinct cohort. Overall, 663 patients had disease progression on anti-CD38 mAb therapy, 466 received further treatment (346 with SoC regimens were included, 120 with investigational agents on clinical trial and were excluded). The median age at initiation of subsequent SoC therapy of 67.9 (range 39.6-89.6) years with a median of 3 prior lines (range 1-9). The median PFS and OS from the start of subsequent therapy was 4.6 (95% CI 4.1-5.6) months and 13.3 (95% CI 10.6-16.6) months, respectively. The median PFS and OS of patients with TCR disease (n = 199) was 4.4 (95% CI 3.6-5.3) months and 10.5 (95% CI 8.5-13.8) months. Our results reinforce that real-world patients with relapsed MM, particularly those with TCR disease, have dismal outcomes. There remains an urgent unmet need for the development of and access to effective therapeutics for these patients.

MK-0457, an Aurora kinase and BCR-ABL inhibitor, is active in patients with BCR-ABL T315I leukemia

MK-0457, an Aurora kinase and BCR-ABL inhibitor, was studied on a Phase I/II study in 77 patients with refractory hematologic malignancies. The average number of cycles per patient was 3 (range 1-21). Maximum tolerated doses for a 5-day short infusion and continuous infusion regimens were 40 mg/m(2)/h and 144 mg/m(2)/h, respectively. Drug-related adverse events (AEs) included transient mucositis and alopecia. Eight of 18 patients with BCR-ABL T315I-mutated chronic myelogenous leukemia (44%) had hematologic responses and one of three patients (33%) with Philadelphia chromosome-positive acute lymphoblastic leukemia obtained complete remission. MK-0457 has important activity in patients with leukemias expressing the highly resistant T315I BCR-ABL mutation.

A phase I clinical and pharmacokinetic (PK) trial of the aurora kinase (AK) inhibitor MK-0457 in cancer patients

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Background: The AKs are essential for mitotic progression, spindle formation, centrosome maturation, chromosomal segregation, and cytokinesis. Elevated expression occurs frequently in tumors. MK-0457 (VX-680) is a potent AK inhibitor, with Ki values of 0.66, 18 and 4.6 nM for AKs A, B and C, respectively. MK-0457 inhibits proliferation of transformed cells in vitro (IC50’s 15–113 nM), and induces colon and pancreatic cancer xenograft regressions. Methods: After IRB approval, consenting patients (pts) with refractory solid tumors (median 3 prior regimens, range 2–6) and adequate hematologic and organ function were enrolled using an accelerated dose escalation scheme with 1–2 pts/dose level until ≥ grade 2 toxicity, followed by 3–6 pts/level. MK-0457 was administered by continuous 5-day intravenous infusion every 28 days. Dose-limiting toxicity (DLT) was grade 3 non-hematologic or grade 4 hematologic toxicity ≥ 5 days, or grade 4 febrile neutropenia (FN) during cycle 1. PKs were collected pre-dose through 168 h and analyzed for MK-0457 and metabolites by HPLC/mass spec. Steady state volume of distribution (Vdss), clearance (CL), maximal concentration (Cmax) and terminal half-life (t1/2) were determined by WinNonLin. Results: 16 pts received MK-0457 dosed at 0.5, 1, 2, 4, 8, and 12 mg/m2/h. Median number of cycles was 2 (range 1–6). DLT was asymptomatic neutropenia ≥ 5 days at 12 mg/m2/h. At 8 mg/m2/h, 1 pt experienced FN in cycle 2; a second developed a grade 2 allergic reaction. Three pts achieved stable disease as best response, and two of them completed 6 cycles. Plasma concentrations reached steady state rapidly (i.e., within 24 h) and declined biexponentially after the end of infusion; after a rapid initial decay, a slower decaying terminal phase demonstrated a t1/2 ∼15 h. PK parameters include Vdss = 237 ± 107 (SD) L/m2 and CL = 517 ± 141 ml/min/m2. At 8 mg/m2/h, Cmax was ∼650 nM. Conclusion: MK-0457 is generally well tolerated and achieves plasma levels similar to those causing regressions in xenografts. CL is high and exposures achieved are roughly dose proportional. Because 8 mg/m2/h was well tolerated in heavily pre-treated pts, escalation to 10 mg/m2/h is underway. Baseline tumor samples will be assessed for predictive biomarkers at the recommended phase II dose.

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Nucleotide analogs and new buffers improve a generalized method to enrich for low abundance mutations

A high sensitivity method for detecting low level mutations is under development. A PCR reaction is performed in which a restriction site is introduced in wild-type DNA by alteration of specific bases. Digestion of wild-type DNA by the cognate restriction endonuclease (RE) enriches for products with mutations within the recognition site. After reamplification, mutations are identified by a ligation detection reaction (LDR). This PCR/RE/LDR assay was initially used to detect PCR error in known wild-type samples. PCR error was measured in low |Deltap K a| buffers containing tricine, EPPS and citrate, as well as otherwise identical buffers containing Tris. PCR conditions were optimized to minimize PCR error using perfect match primers at the Msp I site in the p53 tumor suppressor gene at codon 248. However, since mutations do not always occur within pre-existing restriction sites, a generalized PCR/RE/LDR method requires the introduction of a new restriction site. In principle, PCR with mismatch primers can alter specific bases in a sequence and generate a new restriction site. However, extension from 3' mismatch primers may generate misextension products. We tested conversion of the Msp I (CCGG) site to a Taq I site (TCGA). Conversion was unsuccessful using a natural base T mismatch primer set. Conversion was successful when modified primers containing the 6 H,8 H -3, 4-dihydropyrimido[4,5- c ][1,2]oxazine-7-one (Q6) base at 3'-ends were used in three cycles of preconversion PCR prior to conversion PCR using the 3' natural base T primers. The ability of the pyrimidine analog Q6 to access both a T-like and C-like tautomer appears to greatly facilitate the conversion.

Nucleotide analogs facilitate base conversion with 3' mismatch primers

We compared the efficiency of PCR amplification using primers containing either a nucleotide analog or a mismatch at the 3' base. To determine the distribution of bases inserted opposite eight different analogs, 3' analog primers were used to amplify four different templates. The products from the reactions with the highest amplification efficiency were sequenced. Analogs allowing efficient amplification followed by insertion of a new base at that position are herein termed 'convertides'. The three convertides with the highest amplification efficiency were used to convert sequences containing C, T, G and A bases into products containing the respective three remaining bases. Nine templates were used to generate conversion products, as well as non-conversion control products with no base change. We compared the ability of natural bases to convert specific sites with and without a preconversion step using nucleotide analog primers. Conversion products were identified by a ligation detection reaction using primers specific for the converted sequence. We found that conversions resulting in transitions were easier to accomplish than transversions and that sequence context influences conversion. Specifically, primer slippage appears to be an important mechanism for producing artifacts via polymerase extension of a 3' base or analog transiently base paired to neighboring bases of the template. Nucleotide analogs could often reduce conversion artifacts and increase the yield of the expected product. While new analogs are needed to reliably achieve transversions, the current set have proven effective for creating transition conversions.

NeuroD2 and neuroD3: distinct expression patterns and transcriptional activation potentials within the neuroD gene family

We have identified two new genes, neuroD2 and neuroD3, on the basis of their similarity to the neurogenic basic-helix-loop-helix (bHLH) gene neuroD. The predicted amino acid sequence of neuroD2 shows a high degree of homology to neuroD and MATH-2/NEX-1 in the bHLH region, whereas neuroD3 is a more distantly related family member. neuroD3 is expressed transiently during embryonic development, with the highest levels of expression between days 10 and 12. neuroD2 is initially expressed at embryonic day 11, with persistent expression in the adult nervous system. In situ and Northern (RNA) analyses demonstrate that different regions of the adult nervous system have different relative amounts of neuroD and neuroD2 RNA. Similar to neuroD, expression of neuroD2 in developing Xenopus laevis embryos results in ectopic neurogenesis, indicating that neuroD2 mediates neuronal differentiation. Transfection of vectors expressing neuroD and neuroD2 into P19 cells shows that both can activate expression through simple E-box-driven reporter constructs and can activate a reporter driven by the neuroD2 promoter region, but the GAP-43 promoter is preferentially activated by neuroD2. The noncongruent expression pattern and target gene specificity of these highly related neurogenic bHLH proteins make them candidates for conferring specific aspects of the neuronal phenotype.

Clinical management using direct and derived parameters

In the past, left heart function was estimated from the level of CVP, clinical information and chest x-ray; cardiac output was estimated from mixed venous oxygen saturation or content. These indirect assessments frequently led to incorrect conclusions and irrationale therapy. Currently, direct and derived hemodynamic parameters have been invaluable in the diagnosis, management, and prognosis in critically ill patients. Continuous mixed venous oxygen saturation monitoring affords yet another valuable parameter to facilitate optimal patient care outcomes.

In vitro and in vivo studies of a promising antileukemic thymidine analogue, 5-hydroxymethyl-2' deoxyuridine

The toxicity and metabolism of a thymidine analogue, 5-hydroxymethyl-2'-deoxyuridine (5HmdUrd) were studied with human leukemia cells (HL-60) and with human platelets. 3 X 10(-5) M 5HmdUrd caused a 50% inhibition in the proliferation of HL-60 cells. The compound was hydrolyzed to 5-hydroxymethyluracil (5HmUra) by the enzyme thymidine phosphorylase (EC 2.4.2.4) present in leukemia cells; this catabolic product was non-toxic. The catabolism of 5HmdUrd by human platelet thymidine phosphorylase could be inhibited by 6-aminothymine. The toxicity of 5HmdUrd was effectively reversed by deoxycytidine and 5HmdUrd increased the incorporation of deoxycytidine into dCTP and DNA several fold. The two latter phenomena are explicable in terms of a feedback action to ribonucleotide reductase, resulting in deoxycytidylate starvation, which is a known effect of excess thymidine. We report here also our preliminary observations that 5HmdUrd is active against mouse leukemia in vivo.

5-Ethyl-2'-deoxyuridine. Cytotoxicity and DNA incorporation demonstrated with human leukemic cells and PHA-stimulated lymphocytes in vitro

5-Ethyl-2'-deoxyuridine (5EtdUrd) is a biologically active thymidine analogue. The cytotoxicity of 5EtdUrd was investigated with seven established human leukemia cell lines as well as with human peripheral blood PHA-stimulated lymphocytes. All types of leukemia cells were susceptible to the toxicity of 5EtdUrd as assayed with a [U-14C]-L-leucine incorporation system developed for this study. A 50% inhibition of leucine incorporation in 3-day cultures was induced by 1.3-3.8 microM 5EtdUrd with leukemic cells, but the concentration required to induce similar inhibition with PHA-stimulated lymphocytes was approximately was approximately 100-fold. The toxicity of 5EtdUrd seemed to require active DNA synthesis, since the inhibition of leucine incorporation became obvious only after the first 24 hours of culture. The DNA incorporation studies were based on a new isotopically labeled 5EtdUrd derivative, [2-14C]5EtdUrd, synthesized for this study in our laboratory. It was demonstrated for the first time that most of the radioactivity derived from [2-14C]5EtdUrd in DNA was in 5-ethyluracil. 5EtdUrd has a powerful antileukemic potency in vitro. Its effects against human leukemia in vivo remain to be tested.

Mutagens in feces from vegetarians and non-vegetarians

Mutagens in water extracts from feces of persons in 3 different diet groups were measured with the fluctuation test for weak mutagens using Salmonella typhimurium TA100 and TA98 as tester strains. The 3 diet groups were ovo-lacto vegetarians (N = 6), strict vegetarians (N = 11) and non-vegetarians (N = 12). All subjects were from the urban area of Vancouver, British Columbia, Canada. On TA100 ovo-lacto vegetarians and strict vegetarians had significantly lower levels of fecal mutagens than non-vegetarians (P less than or equal to 0.025 and P less than 0.010, resp.). The same pattern, although less significant, was obtained with TA98. Correlation studies between mutagenicity on TA100 and TA98 and between the pH of the fecal homogenate and mutagenicity indicate the presence of 2 or more major fecal mutagens.