OSWG Recommended Approaches to the Nonclinical Pharmacokinetic (ADME) Characterization of Therapeutic Oligonucleotides

This white paper summarizes the recommendations of the absorption, distribution, metabolism, and excretion (ADME) Subcommittee of the Oligonucleotide Safety Working Group for the characterization of absorption, distribution, metabolism, and excretion of oligonucleotide (ON) therapeutics in nonclinical studies. In general, the recommended approach is similar to that for small molecule drugs. However, some differences in timing and/or scope may be warranted due to the greater consistency of results across ON classes as compared with the diversity among small molecule classes. For some types of studies, a platform-based approach may be appropriate; once sufficient data are available for the platform, presentation of these data should be sufficient to support development of additional ONs of the same platform. These recommendations can serve as a starting point for nonclinical study design and foundation for discussions with regulatory agencies.

Phase 1 trial evaluating MRG-106, a synthetic inhibitor of microRNA-155, in patients with cutaneous t-cell lymphoma (CTCL)

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Background: MRG-106 is an oligonucleotide inhibitor of miR-155, a microRNA with a strong mechanistic link to CTCL, selected based on its activity in mycosis fungoides (MF) cell lines. The objective of this first-in-human study is to evaluate the safety, tolerability, maximum tolerated dose (MTD), pharmacokinetics (PK), and preliminary efficacy of MRG-106 in MF patients. Methods: This Phase 1 trial employs a dose-escalation design to evaluate either intratumoral (IT, 75 mg/dose) or subcutaneous (SC, ≤ 900 mg/dose) administration of MRG-106. Patients were required to have biopsy-proven stage I-III MF and plaque- or tumor-stage lesions. Results: Fifteen patients (12M/3F, median age 59 years) have been dosed over 1-4 weeks. All patients tolerated the IT or SC administrations well with only minor local injection reactions in 8 patients. Thirteen of 15 patients completed dosing as scheduled. There were no clinically significant MRG-106 related adverse events with the exception of one grade 3 pruritus. The MTD has not yet been reached. In the IT cohort, a reduction of ≥50% in the baseline Composite Assessment of Index Lesion Severity (CAILS) score was observed in the MRG-106 treated lesions in all 4 evaluable patients who completed dosing; such responses were maintained to the End of Study visit (Day 28 or 35). Histological examination of pre- and post-treatment biopsies of the MRG-106-injected lesion from most patients revealed a trend in reduction in neoplastic cell density and depth; 1 patient had a complete loss of the neoplastic infiltrate. Gene expression analysis of the pre- and post-treatment biopsies showed reduction of the PI3K/AKT, JAK/STAT, and NFkB survival pathways and increased cell death consistent with the expected MRG-106 mechanism of action. In the SC cohorts, 3/8 patients had a maximal decrease in their modified Severity-Weighted Assessment Tool (mSWAT) of > 39% indicative of a significant response. One patient at the 900 mg SC dose level had a possible flare of their disease after 3 doses that resolved after 3 weeks. Conclusions: Based on favorable clinical safety, efficacy and PK data, additional patients are being accrued. Updated results will be presented as available. Clinical trial information: NCT02580552.

Miniaturized hemoproteins

The present paper highlights and reviews current research in the field of hemoprotein models. Hemoproteins have been extensively studied in order to understand structure-function relationships, and to design new molecules with desired functions. A wide number of synthetic analogues have been developed, using quite different approaches. They differ in molecular structures, ranging from simple meso-substituted tetraaryl-metalloporphyrins and peptide-porphyrin conjugates. In this paper we summarize the state of the art on peptide based hemoprotein models. We also report here the approach used by us to develop a new class of molecules, named mimochromes. They can be regarded as miniaturized hemoproteins, because mimochromes are low molecular weight compounds with some structural and functional properties common to those of the parent high molecular weight protein. The basic structure of mimochromes is a deuteroporphyrin ring covalently linked to two helical peptide chains. Two molecules of this series have been fully characterized. All the information derived from their structural analysis has been applied to the design of new analogues with additional functions.

Phosphatidylinositol-specific phospholipase C isoform expression in pregnant and nonpregnant rat myometrial tissue

OBJECTIVE

Activation of the phosphatidylinositol signaling pathway plays a significant role during the intracellular signal transduction events activated during agonist-stimulated phasic myometrial contractions. Phospholipase C is an essential molecular component of this signaling pathway. These studies sought to characterize the expression of phospholipase C isoform messenger ribonucleic acid in both pregnant and nonpregnant rat myometrium.

STUDY DESIGN

Total cellular ribonucleic acid was isolated from myometrial tissue collected from Sprague-Dawley rats by use of the acidic guanidinium thiocyanate-phenol-chloroform extraction technique. After deoxyribonuclease treatment to ensure removal of genomic deoxyribonucleic acid, as well as resolution on formaldehyde-1% agarose horizontal slab gels to rule out degradation, the ribonucleic acid was used for semiquantitative competitive reverse transcriptase-polymerase chain reaction studies to evaluate the expression of five of the reported phospholipase C isoforms. These studies were performed with isoform-specific 20-mer primers and the inclusion of internal standard heterologous deoxyribonucleic acid sequences designed with ends homologous to the isoform-specific primers. The identity of the polymerase chain reaction products was confirmed with restriction endonuclease digestions and homology analysis of the sequenced polymerase chain reaction product deoxyribonucleic acid.

RESULTS

These reverse transcriptase-polymerase chain reaction studies have confirmed expression of the phospholipase C-beta1a, phospholipase C-beta3, phospholipase C-gamma1, phospholipase C-beta2, and phospholipase C-delta1 isoforms in rat myometrial tissue. During pregnancy the levels of expression of the phospholipase C-beta3, phospholipase C-gamma1, and phospholipase C-delta1 isoforms were increased compared with the levels of expression in myometrium from nonpregnant rats. In myometrium from both pregnant and nonpregnant animals the phospholipase C-beta1 a isoform was expressed at the highest level, the phospholipase C-beta3, phospholipase C-gamma1, and phospholipase C-gamma2 isoforms at an intermediate level, and the phospholipase C-delta1 isoform was expressed at the lowest levels.

CONCLUSIONS

These studies have confirmed at the messenger ribonucleic acid level significant expression of several isoforms of phospholipase C in both pregnant and nonpregnant myometrial tissue. These observations provide additional support for the hypothesis that the phosphatidylinositol signaling pathway plays an important role in uterine smooth muscle.

Beta-adrenergic receptor subtype gene expression in timed-pregnant rat myometrium

OBJECTIVE

Classic radioligand binding techniques have suggested that beta 1- and beta 2-adrenergic receptor subtype proteins are expressed in myometrial tissue; however, to date these observations have not been confirmed at the level of the messenger ribonucleic acid for these clinically important membrane receptors. The studies described in this report sought to use quantitative reverse transcriptase-polymerase chain reaction techniques to confirm expression of messenger ribonucleic acid for the beta 1- and beta 2-adrenergic receptors in myometrial tissue and to determine whether messenger ribonucleic acid expression for these two adrenergic receptors is modulated during pregnancy.

STUDY DESIGN

For these studies total cellular ribonucleic acid was isolated from myometrial tissue obtained from timed-pregnant Sprague-Dawley rats by the guanidium thiocyanate-phenol-chloroform extraction technique; formaldehyde-agarose gels then confirmed isolation of intact ribonucleic acid. Random hexamers and reverse transcriptase were used to synthesize complementary deoxyribonucleic acid. Subsequently, polymerase chain reaction was performed with subtype specific 20-mer sense and antisense oligonucleotide primers specific for the rat beta 1- and beta 2-adrenergic receptors. Inclusion of internal standard deoxyribonucleic acid sequences allowed quantification of the reverse transcriptase-polymerase chain reaction results.

RESULTS

By use of total cellular ribonucleic acid isolated from myometrial tissue, reverse transcriptase-polymerase chain reaction generated the expected 328 bp product for the beta 1-receptor and the expected 559 bp product for the beta 2-receptor along with internal standard deoxyribonucleic acid sequences for both. The identity of the beta 1- and beta 2-adrenergic receptor polymerase chain reaction products was confirmed on the basis of restriction endonuclease digestions producing the expected deoxyribonucleic acid fragments and by Southern blots using beta 1- and beta 2-adrenergic receptor-specific complementary deoxyribonucleic acid probes. The reverse transcriptase-polymerase chain reaction studies confirmed a gradual decline in beta 1-receptor messenger ribonucleic acid and stable expression of beta 2-receptor messenger ribonucleic acid during the second half of gestation in pregnant rat myometrial tissue.

CONCLUSIONS

In summary, these studies have confirmed, at the messenger ribonucleic acid level, expression of the beta 1- and beta 2-adrenergic receptor subtypes in timed-pregnant rat myometrial tissue.