Predicting the pharmacokinetics and pharmacodynamics of antisense oligonucleotides: an overview of various approaches and opportunities for PBPK/PD modelling.

INTRODUCTION: Advances in research and development (R&D) have enabled many approvals of antisense oligonucleotides (ASOs). Its administration expanded from systemic to local for treating various diseases, where predicting target tissue exposures and pharmacokinetics (PK) and pharmacodynamics (PD) in human can be critical. AREAS COVERED: A literature search for PBPK/PD models of ASOs was conducted using PubMed and Embase (to 1 April 2023). ASO PK and PD in animals and humans and modeling approaches including physiologically based (PB) are summarized; and relevance and impacts of PBPK/PD modeling are assessed. EXPERT OPINION: Allometric scaling and compartmental PK/PD modeling have been successful to predict human ASO PK/PD, addressing most R&D needs. Understanding tissue distribution of ASOs can be crucial for their efficacy and safety especially for intrathecal (IT), pulmonary, or other local routes. PBPK/PD modeling is expected to improve such understanding, for which, efforts have been sporadic. However, developing a PBPK/PD model requires careful review of known biology/pharmacology and thoughtful experimental designs. Resulting models have the potential to predict target/specified tissue exposures and responses in human adults and pediatrics. Ultimately, a PBPK/PD modeling approach can lead to more efficient and rational clinical development, resulting in well-informed decision making and a shortened timeline.

Assessment of the Effect of Organ Impairment on the Pharmacokinetics of 2'-MOE and Phosphorothioate Modified Antisense Oligonucleotides.

The pharmacokinetics (PK) of 2'-O-methoxyethyl and phosphorothioate antisense oligonucleotides (ASOs), with or without N-acetyl galactosamine conjugation, have been well characterized following subcutaneous or intravenous drug administration. However, the effect of organ impairment on ASO PK, primarily hepatic or renal impairment, has not yet been reported. ASOs distribute extensively to the liver and kidneys, where they are metabolized slowly by endo- and exonucleases, with minimal renal excretion as parent drug (<1%-3%). This short review evaluated the effect of organ impairment on ASO PK using 3 case studies: (1) a phase 1 renal impairment study evaluating a N-acetyl galactosamine-conjugated ASO in healthy study participants and study participants with moderate renal impairment, (2) a phase 2 study evaluating an unconjugated ASO in patients with end-stage renal disease; and (3) a phase 3 study evaluating an unconjugated ASO, which included patients with mild hepatic or renal impairment. Results showed that patients with end-stage renal disease had a mild increase (≈34%) in total plasma exposure, whereas mild or moderate renal impairment showed no effect on plasma PK. The effect of hepatic impairment on ASO PK could not be fully evaluated due to lack of data in moderate and severe hepatic impairment study participants. Nonetheless, available data suggest that mild hepatic impairment had no effect on ASO exposure.

Population pharmacokinetic/pharmacodynamic modelling of eplontersen, an antisense oligonucleotide in development for transthyretin amyloidosis.

AIMS: Transthyretin-mediated amyloidosis is a progressive and fatal disease caused by the build-up of misfolded transthyretin (TTR) protein. Eplontersen is a triantennary N-acetyl galactosamine (GalNAc3)-conjugated antisense oligonucleotide targeting TTR messenger ribonucleic acid (mRNA) to inhibit production of both variant and wild-type TTR. We aimed to develop a population pharmacokinetic/pharmacodynamic (PK/PD) model for eplontersen and to evaluate the impact of covariates on exposure and response. METHODS: Plasma eplontersen and serum TTR concentration data were obtained from two phase 1 studies in healthy volunteers (ClinicalTrials.gov: NCT03728634, NCT04302064). Model development was conducted using a nonlinear mixed-effects approach. RESULTS: Eplontersen PK was well described by a two-compartment model. Evaluation of demographics identified significant covariates of lean body mass on clearance and body weight on intercompartmental clearance and volumes of distribution. Population PK modelling showed the absorption rate was 29.6% greater with injection into the abdomen versus the arm. The typical population terminal elimination half-life was 25.5 days. Serum TTR was well described by an indirect response model with inhibition of TTR production by eplontersen. Maximum fractional inhibition (Imax ) was 0.970 (0.549%RSE) and the half maximal inhibitory concentration (IC50 ) was 0.0283 ng/ml (13.3%RSE). Simulations showed subjects with lower weight had higher exposure (AUC, Cmax ), while higher Cmax was observed when comparing site of administration (ratio abdomen/arm = 1.18), but differences in exposure did not significantly impact response at evaluated doses. CONCLUSION: The exposure-response relationship of eplontersen was well characterised by the PKPD model. Weight and injection site were found to affect systemic exposure, but this effect does not seem to result in clinically relevant variation in response.

Phase 2 Study of the Factor XI Antisense Inhibitor IONIS-FXIRx in Patients With ESRD.

INTRODUCTION: Patients with end-stage renal disease (ESRD) requiring hemodialysis (HD) have an increased risk of thrombotic events and bleeding. Antisense reduction of factor XI (FXI) with IONIS-FXIRx is a novel strategy that may safely reduce the risk of thrombotic events. METHODS: This multicenter study enrolled 49 patients receiving HD in 2 parts. First, 6 participants (pharmacokinetics [PK] cohort) received 1 open-label 300 mg dose of IONIS-FXIRx both before and after HD. Subsequently, 43 participants were treated in a double-blind, randomized design with 200 mg or 300 mg IONIS-FXIRx or placebo for 12 weeks. The PK, pharmacodynamics (PD), and adverse events of IONIS-FXIRx were evaluated (ClinicalTrials.gov: NCT02553889). RESULTS: The PK of IONIS-FXIRx was consistent with previous studies and similar whether injected before or after HD. No accumulation of IONIS-FXIRx was observed after repeat administration. By day 85, mean levels of FXI activity fell 56.0% in the 200 mg group, 70.7% in the 300 mg group, and 3.9% in the placebo group compared with baseline. FXI antigen levels paralleled FXI activity. Dose-dependent prolongation of activated partial thromboplastin time (aPTT) was observed, with no changes in international normalized ratio (INR). IONIS-FXIRx was not associated with drug-related serious adverse events. In the randomized phase of the study, major bleeding events occurred in 0 (0.0%; 200 mg), 1 (6.7%; 300 mg), and 1 (7.7%; placebo) patients and were not considered related to treatment. CONCLUSION: IONIS-FXIRx reduced FXI activity in patients with ESRD receiving HD. Further studies are needed to determine the benefit-risk profile of FXI as a therapeutic target for patients who require HD.

PK/PD modeling of FXI antisense oligonucleotides to bridge the dose-FXI activity relation from healthy volunteers to end-stage renal disease patients.

IONIS-FXIRX (BAY2306001) is an antisense oligonucleotide that inhibits the synthesis of coagulation factor XI (FXI) and has been investigated in healthy volunteers and patients with end-stage renal disease (ESRD). FXI-LICA (BAY2976217) shares the same RNA sequence as IONIS-FXIRX but contains a GalNAc-conjugation that facilitates asialoglycoprotein receptor (ASGPR)-mediated uptake into hepatocytes. FXI-LICA has been studied in healthy volunteers and is currently investigated in patients with ESRD on hemodialysis. We present a model-informed bridging approach that facilitates the extrapolation of the dose-exposure-FXI relationship from IONIS-FXIRX to FXI-LICA in patients with ESRD and, thus, supports the selection of FX-LICA doses being investigated in patients with ESRD. A two-compartment pharmacokinetic (PK) model, with mixed first- and zero-order subcutaneous absorption and first-order elimination, was combined with an indirect response model for the inhibitory effect on the FXI synthesis rate via an effect compartment. This PK/pharmacodynamic model adequately described the median trends, as well as the interindividual variabilities for plasma drug concentration and FXI activity in healthy volunteers of IONIS-FXIRX and FXI-LICA, and in patients with ESRD of IONIS-FXIRX . The model was then used to predict dose-dependent steady-state FXI activity following repeat once-monthly doses of FXI-LICA in a virtual ESRD patient population. Under the assumption of similar ASGPR expression in patients with ESRD and healthy volunteers, doses of 40 mg, 80 mg, and 120 mg FXI-LICA are expected to cover the target range of clinical interest for steady-state FXI activity in the phase IIb study of FXI-LICA in patients with ESRD undergoing hemodialysis.

An oral antisense oligonucleotide for PCSK9 inhibition.

Inhibitors of proprotein convertase subtilisin/kexin type 9 (PCSK9) reduce low-density lipoprotein (LDL) cholesterol and are used for treatment of dyslipidemia. Current PCSK9 inhibitors are administered via subcutaneous injection. We present a highly potent, chemically modified PCSK9 antisense oligonucleotide (ASO) with potential for oral delivery. Past attempts at oral delivery using earlier-generation ASO chemistries and transient permeation enhancers provided encouraging data, suggesting that improving potency of the ASO could make oral delivery a reality. The constrained ethyl chemistry and liver targeting enabled by N-acetylgalactosamine conjugation make this ASO highly potent. A single subcutaneous dose of 90 mg reduced PCSK9 by >90% in humans with elevated LDL cholesterol and a monthly subcutaneous dose of around 25 mg is predicted to reduce PCSK9 by 80% at steady state. To investigate the feasibility of oral administration, the ASO was coformulated in a tablet with sodium caprate as permeation enhancer. Repeated oral daily dosing in dogs resulted in a bioavailability of 7% in the liver (target organ), about fivefold greater than the plasma bioavailability. Target engagement after oral administration was confirmed by intrajejunal administration of a rat-specific surrogate ASO in solution with the enhancer to rats and by plasma PCSK9 and LDL cholesterol lowering in cynomolgus monkey after tablet administration. On the basis of an assumption of 5% liver bioavailability after oral administration in humans, a daily dose of 15 mg is predicted to reduce circulating PCSK9 by 80% at steady state, supporting the development of the compound for oral administration to treat dyslipidemia.

Ligand conjugated antisense oligonucleotide for the treatment of transthyretin amyloidosis: preclinical and phase 1 data.

AIMS: Amyloidogenic transthyretin (ATTR) amyloidosis is a fatal disease characterized by progressive cardiomyopathy and/or polyneuropathy. AKCEA-TTR-LRx (ION-682884) is a ligand-conjugated antisense drug designed for receptor-mediated uptake by hepatocytes, the primary source of circulating transthyretin (TTR). Enhanced delivery of the antisense pharmacophore is expected to increase drug potency and support lower, less frequent dosing in treatment. METHODS AND RESULTS: AKCEA-TTR-LRx demonstrated an approximate 50-fold and 30-fold increase in potency compared with the unconjugated antisense drug, inotersen, in human hepatocyte cell culture and mice expressing a mutated human genomic TTR sequence, respectively. This increase in potency was supported by a preferential distribution of AKCEA-TTR-LRx to liver hepatocytes in the transgenic hTTR mouse model. A randomized, placebo-controlled, phase 1 study was conducted to evaluate AKCEA-TTR-LRx in healthy volunteers (ClinicalTrials.gov: NCT03728634). Eligible participants were assigned to one of three multiple-dose cohorts (45, 60, and 90 mg) or a single-dose cohort (120 mg), and then randomized 10:2 (active : placebo) to receive a total of 4 SC doses (Day 1, 29, 57, and 85) in the multiple-dose cohorts or 1 SC dose in the single-dose cohort. The primary endpoint was safety and tolerability; pharmacokinetics and pharmacodynamics were secondary endpoints. All randomized participants completed treatment. No serious adverse events were reported. In the multiple-dose cohorts, AKCEA-TTR-LRx reduced TTR levels from baseline to 2 weeks after the last dose of 45, 60, or 90 mg by a mean (SD) of -85.7% (8.0), -90.5% (7.4), and -93.8% (3.4), compared with -5.9% (14.0) for pooled placebo (P < 0.001). A maximum mean (SD) reduction in TTR levels of -86.3% (6.5) from baseline was achieved after a single dose of 120 mg AKCEA-TTR-LRx . CONCLUSIONS: These findings suggest an improved safety and tolerability profile with the increase in potency achieved by productive receptor-mediated uptake of AKCEA-TTR-LRx by hepatocytes and supports further development of AKCEA-TTR-LRx for the treatment of ATTR polyneuropathy and cardiomyopathy.

Immunogenicity Assessment of Inotersen, a 2'-O-(2-Methoxyethyl) Antisense Oligonucleotide in Animals and Humans: Effect on Pharmacokinetics, Pharmacodynamics, and Safety.

Inotersen (TEGSEDI™) is a 2'-O-(2-methoxyethyl)-modified antisense oligonucleotide, intended for treating hereditary transthyretin (TTR) amyloidosis with polyneuropathy. The potential immunogenicity (IM) response to inotersen was evaluated in chronic nonclinical safety studies and the pivotal phase 2/3 clinical study. The evaluation was designed to assess the characteristics of antidrug antibodies (ADAs) and their effects on the pharmacokinetics, pharmacodynamics, clinical efficacy, and safety in animals and humans. No immunogenic response was observed after long-term treatment with inotersen in mice. In monkeys, the incidence rate of IM to inotersen appeared to be dose dependent, with 28.6%-50.0% of animals developing ADAs after 36 weeks of treatment. This was characterized as late onset (median onset of 185 days) with low titers (median titer of 8, or 400 if minimum required dilution of 50 is included). The overall incidence rate of patients who developed ADAs was 30% after 65 weeks of treatment with median onset of 203 days and median peak titer of 300. IM had minimal effect on plasma peak (Cmax) and total exposure (i.e. area under curve, AUC) of inotersen, but showed elevated plasma trough levels in both IM-positive animals and humans. However, ADAs had no effect on tissue exposure, TTR messenger RNA, or plasma TTR levels in the long-term monkey study. Similarly, IM showed no effect on plasma TTR levels in clinical studies. Thus, ADAs antibodies were binding antibodies, but not neutralizing antibodies. Finally, no association was observed between IM and toxicity findings (eg, platelet, complement activation, and histopathology findings) in the inotersen 9-month monkey study. In humans, no difference was observed in hematology, including platelets, kidney function tests, or incidence of adverse events between IM-positive and -negative patients. Overall, IM showed no effect on toxicity or safety of inotersen evaluated in both monkeys and humans. ClinicalTrials.gov Identifier: NCT01737398.

Population Pharmacokinetic-Pharmacodynamic Modeling of Inotersen, an Antisense Oligonucleotide for Treatment of Patients with Hereditary Transthyretin Amyloidosis.

A population pharmacokinetic (PK) and pharmacodynamic (PD) model was developed for inotersen to evaluate exposure-response relationships and to optimize therapeutic dosing regimen in patients with hereditary transthyretin (TTR) amyloidosis polyneuropathy (hATTR-PN). Inotersen PK and TTR level (PD) data were composed of one Phase 1 study in healthy subjects, one Phase 2/3 study in hATTR patients, and its one open-label extension study. Effects of intrinsic and extrinsic factors (covariates) on PK and PK/PD of inotersen were evaluated using a full model approach. Inotersen PK was characterized by a two-compartment model with elimination from the central compartment. The population PK analysis identified disease status and lean body mass (LBM) as significant covariates for inotersen PK. Nonetheless, the contribution of disease status and LBM on PK was small, as the difference in clearance (CL/F) was 11.1% between healthy subjects and patients with hATTR-PN and 38% between the lowest and highest LBM quartiles of the patient population. Age, race, sex, baseline renal function estimated glomerular filtration rate, and hepatic function markers (baseline albumin, bilirubin, and alanine aminotransferase values) were not statistically significant covariates affecting inotersen PK. An inhibitory effect indirect-response model (inhibition of TTR production) was used to describe the drug effect on TTR-time profiles, with baseline TTR included as a covariate. The overall population Imax and IC50, together with 95% confidence interval, was estimated to be 0.913 (0.899-0.925) and 9.07 (8.08-10.1) ng/mL, respectively. V30M mutation showed no effect on the estimated IC50 value for hATTR patients. The final population PK and PK/PD model was used to simulate four different treatment regimens. The population PK/PD model developed well described the PK and PD of inotersen in patients with hATTR-PN and has been used for label recommendation and trial simulations.

Pharmacokinetics and Clinical Pharmacology Considerations of GalNAc3-Conjugated Antisense Oligonucleotides.

Introduction: Triantennary N-acetyl galactosamine (GalNAc3) - conjugated antisense oligonucleotides (ASOs) have demonstrated improved hepatocyte uptake and pharmacologic activity over their parent unconjugated ASOs in animals and humans. Areas covered: In this review, the ADME (absorption, distribution, metabolism, and excretion) characteristics of GalNAc3-conjugated ASOs in animals and in humans are summarized, and their clinical relevance is evaluated from the clinical pharmacology perspectives. Expert opinion: ASOs distribute to tissues via receptor-mediated processes, and conjugation to a ligand specific to certain cell types can improve target tissue delivery. GalNAc3-conjugation represents a good example on this regard and has demonstrated ideal characteristics of a prodrug to target delivery of ASOs to hepatocytes via the asialoglycoprotein receptor (ASGPR). The improved potency and safety margin permit more flexible dosing (e.g. monthly or less frequently if needed) taking full advantage of the long half-life of the parent ASO in humans. However, while still speculative, it should be noted that ASGPR-mediated uptake could become nonlinear with dose and factors that impact ASGPR expression or compete with ASGPR-mediated uptake could potentially affect the uptake of GalNAc3-conjugated ASOs, further studies are warranted.

Integrated Assessment of the Clinical Performance of GalNAc3-Conjugated 2'-O-Methoxyethyl Chimeric Antisense Oligonucleotides: I. Human Volunteer Experience.

Advances in medicinal chemistry have produced new chemical classes of antisense oligonucleotides (ASOs) with enhanced therapeutic properties. Conjugation of the triantennary N-acetylgalactosamine (GalNAc3) moiety to the extensively characterized phosphorothioate (PS)-modified 2'-O-methoxyethyl (2'MOE) ASO exemplifies such an advance. This structure-activity optimized moiety effects receptor-mediated uptake of the ASO prodrug through the asialoglycoprotein receptor 1 to support selective targeting of RNAs expressed by hepatocytes. In this study we report the integrated assessment of data available from randomized placebo-controlled dose-ranging studies of this chemical class of ASOs administered systemically to healthy human volunteers. First, we compare the pharmacokinetic and pharmacodynamic profiles of a subset of the GalNAc3-conjugated PS-modified 2'MOE ASOs to the parent PS-modified 2'MOE ASOs for which plasma analytes are available. We then evaluate the safety profile of the full set of GalNAc3-conjugated PS-modified 2'MOE ASO conjugates by the incidence of signals in standardized laboratory tests and by the mean laboratory test results as a function of dose level over time. With hepatocyte targeted delivery, the ED50 for the GalNAc3-conjugated PS-modified 2'MOE ASO subset ranges from 4 to 10 mg/week, up to 30-fold more potent than the parent PS-modified 2'MOE ASO. No GalNAc3-conjugated PS-modified 2'MOE ASO class effects were identified from the assessment of the integrated laboratory test data across all doses tested with either single or multidose regimens. The increase in potency supports an increase in the safety margin for this new chemical class of ASOs now under broad investigation in the clinic. Although the total exposure is limited in the initial phase 1 trials, ongoing and future investigations in patient populations will support evaluation of the effects of long-term exposure.

Assessment of the Drug Interaction Potential of Unconjugated and GalNAc3-Conjugated 2'-MOE-ASOs.

Antisense oligonucleotides are metabolized by nucleases and drug interactions with small drug molecules at either the cytochrome P450 (CYP) enzyme or transporter levels have not been observed to date. Herein, a comprehensive in vitro assessment of the drug-drug interaction (DDI) potential was carried out with four 2'-O-(2-methoxyethyl)-modified antisense oligonucleotides (2'-MOE-ASOs), including a single triantennary N-acetyl galactosamine (GalNAc3)-conjugated ASO. Several investigations to describe the DDI potential of a 2'-MOE-ASO conjugated to a high-affinity ligand for hepatocyte-specific asialoglycoprotein receptors are explored. The inhibition on CYP1A2, CYP2B6, CYP2C8, CYP2C9, CYP2C19, CYP2D6, CYP2E1, and CYP3A4 and induction on CYP1A2, CYP2B6, and CYP3A4 were investigated in cryopreserved hepatocytes using up to 100 µM of each ASO. No significant inhibition (half maximal inhibitory concentration [IC50] > 100 µM) or induction was observed based on either enzymatic phenotype or mRNA levels. In addition, transporter interaction studies were conducted with nine major transporters per recommendations from regulatory guidances and included three hepatic uptake transporters, organic cation transporter 1 (OCT1), organic anion transporting polypeptide 1B1 (OATP1B1), and OATP1B3; three renal uptake transporters, organic anion transporter 1 (OAT1), OAT3, and OCT2; and three efflux transporters, P-glycoprotein (P-gp), breast cancer resistance protein (BCRP), and bile salt export pump (BSEP). None of the four ASOs (10 µM) were substrates of any of the nine transporters, with uptake <2-fold compared to controls, and efflux ratios were below 2.0 for BCRP and P-gp. Additionally, neither of the four ASOs showed meaningful inhibition on any of the nine transporters tested, with the mean percent inhibition ranging from -38.3% to 24.2% with 100 µM ASO. Based on these findings, the unconjugated and GalNAc3-conjugated 2'-MOE-ASOs would have no or minimal DDI with small drug molecules via any major CYP enzyme or drug transporters at clinically relevant exposures.

Lack of QT Prolongation for 2'-O-Methoxyethyl-Modified Antisense Oligonucleotides Based on Retrospective Exposure/Response Analysis of Ten Phase 1 Dose-Escalation Placebo-Controlled Studies in Healthy Subjects.

The potential of QT prolongation of ten 2'-O-methoxyethyl-modified (2'-MOE) antisense oligonucleotides (ASOs) was evaluated retrospectively via exposure/response (ER) analysis using data from Phase 1 clinical studies in healthy subjects. All Phase 1 studies were double-blind, placebo-controlled, single and multiple ascending dose studies designed to assess the safety, tolerability, pharmacokinetics (PK), and pharmacodynamics of the ASOs in healthy subjects. The active doses in these studies ranged from 50 to 450 mg administered by subcutaneous (SC) injection in single and multiple ascending dose cohorts. Two of the ten studies also included 2-h intravenous (IV) infusions up to 600 mg. Electrocardiogram (ECG) measurements were performed at baseline and selected time points (including Tmax). The correlation between QTcF intervals corrected for baseline (ΔQTcF) and the mean time-matched placebo (ΔΔQTcF) with PK plasma exposure when available was evaluated using a linear mixed-effects approach. There was no evidence for QTc prolongation associated with increasing plasma concentrations in healthy subjects, including exposures with treatment up to 450 mg administered SC or 600 mg by IV infusions, and concentrations that are 4-20 times the Cmax of the therapeutic dose, as assessed by both ΔQTcF and ΔΔQTcF. The ER analysis of the relationship between drug plasma concentration and ΔΔQTcF showed that the slope of the regression line was close to zero, and the upper bound of the 90% confidence interval at twice the mean observed (or predicted) Cmax (2 × Cmax) of the clinical therapeutic dose (ie, the highest clinically relevant plasma concentration) was well below 10 ms for all 10 compounds evaluated. Therefore, no concentration-dependent effect on QT prolongation was observed for any one of the ten 2'-MOE ASOs evaluated in Phase 1 studies. These results confirmed that 2'-MOE ASOs, as a chemical class, do not cause QT prolongation at clinically relevant dose levels.

Antisense oligonucleotides targeting apolipoprotein(a) in people with raised lipoprotein(a): two randomised, double-blind, placebo-controlled, dose-ranging trials.

BACKGROUND: Elevated lipoprotein(a) (Lp[a]) is a highly prevalent (around 20% of people) genetic risk factor for cardiovascular disease and calcific aortic valve stenosis, but no approved specific therapy exists to substantially lower Lp(a) concentrations. We aimed to assess the efficacy, safety, and tolerability of two unique antisense oligonucleotides designed to lower Lp(a) concentrations. METHODS: We did two randomised, double-blind, placebo-controlled trials. In a phase 2 trial (done in 13 study centres in Canada, the Netherlands, Germany, Denmark, and the UK), we assessed the effect of IONIS-APO(a)Rx, an oligonucleotide targeting apolipoprotein(a). Participants with elevated Lp(a) concentrations (125-437 nmol/L in cohort A; ≥438 nmol/L in cohort B) were randomly assigned (in a 1:1 ratio in cohort A and in a 4:1 ratio in cohort B) with an interactive response system to escalating-dose subcutaneous IONIS-APO(a)Rx (100 mg, 200 mg, and then 300 mg, once a week for 4 weeks each) or injections of saline placebo, once a week, for 12 weeks. Primary endpoints were mean percentage change in fasting plasma Lp(a) concentration at day 85 or 99 in the per-protocol population (participants who received more than six doses of study drug) and safety and tolerability in the safety population. In a phase 1/2a first-in-man trial, we assessed the effect of IONIS-APO(a)-LRx, a ligand-conjugated antisense oligonucleotide designed to be highly and selectively taken up by hepatocytes, at the BioPharma Services phase 1 unit (Toronto, ON, Canada). Healthy volunteers (Lp[a] ≥75 nmol/L) were randomly assigned to receive a single dose of 10-120 mg IONIS-APO(a)LRx subcutaneously in an ascending-dose design or placebo (in a 3:1 ratio; single-ascending-dose phase), or multiple doses of 10 mg, 20 mg, or 40 mg IONIS-APO(a)LRx subcutaneously in an ascending-dose design or placebo (in an 8:2 ratio) at day 1, 3, 5, 8, 15, and 22 (multiple-ascending-dose phase). Primary endpoints were mean percentage change in fasting plasma Lp(a) concentration, safety, and tolerability at day 30 in the single-ascending-dose phase and day 36 in the multiple-ascending-dose phase in participants who were randomised and received at least one dose of study drug. In both trials, the randomised allocation sequence was generated by Ionis Biometrics or external vendor with a permuted-block randomisation method. Participants, investigators, sponsor personnel, and clinical research organisation staff who analysed the data were all masked to the treatment assignments. Both trials are registered with ClinicalTrials.gov, numbers NCT02160899 and NCT02414594. FINDINGS: From June 25, 2014, to Nov 18, 2015, we enrolled 64 participants to the phase 2 trial (51 in cohort A and 13 in cohort B). 35 were randomly assigned to IONIS-APO(a)Rx and 29 to placebo. At day 85/99, participants assigned to IONIS-APO(a)Rx had mean Lp(a) reductions of 66·8% (SD 20·6) in cohort A and 71·6% (13·0) in cohort B (both p<0·0001 vs pooled placebo). From April 15, 2015, to Jan 11, 2016, we enrolled 58 healthy volunteers to the phase 1/2a trial of IONIS-APO(a)-LRx. Of 28 participants in the single-ascending-dose phase, three were randomly assigned to 10 mg, three to 20 mg, three to 40 mg, six to 80 mg, six to 120 mg, and seven to placebo. Of 30 participants in the multiple-ascending-dose phase, eight were randomly assigned to 10 mg, eight to 20 mg, eight to 40 mg, and six to placebo. Significant dose-dependent reductions in mean Lp(a) concentrations were noted in all single-dose IONIS-APO(a)-LRx groups at day 30. In the multidose groups, IONIS-APO(a)-LRx resulted in mean reductions in Lp(a) of 66% (SD 21·8) in the 10 mg group, 80% (SD 13·7%) in the 20 mg group, and 92% (6·5) in the 40 mg group (p=0·0007 for all vs placebo) at day 36. Both antisense oligonucleotides were safe. There were two serious adverse events (myocardial infarctions) in the IONIS-APO(a)Rx phase 2 trial, one in the IONIS-APO(a)Rx and one in the placebo group, but neither were thought to be treatment related. 12% of injections with IONIS-APO(a)Rx were associated with injection-site reactions. IONIS-APO(a)-LRx was associated with no injection-site reactions. INTERPRETATION: IONIS-APO(a)-LRx is a novel, tolerable, potent therapy to reduce Lp(a) concentrations. IONIS-APO(a)-LRx might mitigate Lp(a)-mediated cardiovascular risk and is being developed for patients with elevated Lp(a) concentrations with existing cardiovascular disease or calcific aortic valve stenosis. FUNDING: Ionis Pharmaceuticals.

Disposition and Pharmacokinetics of a GalNAc3-Conjugated Antisense Oligonucleotide Targeting Human Lipoprotein (a) in Monkeys.

Triantennary N-acetyl galactosamine (GalNAc3)-conjugated antisense oligonucleotides (ASOs) have greatly improved potency due to receptor-mediated uptake into hepatocyte. The disposition and pharmacokinetics of ISIS 681257, a GalNAc3-conjugated ASO, were studied in monkeys. Following subcutaneous (SC) injection, ISIS 681257 was rapidly absorbed into the systemic circulation, with peak plasma levels observed within hours after dosing. After reaching Cmax, plasma concentrations rapidly declined in a multiexponential manner and were characterized by a dominant initial rapid distribution phase in which drug transferred to tissues from circulation, followed by a much slower terminal elimination phase (half-life of 4 weeks). Intact ISIS 681257 is the major full-length oligonucleotide species in plasma (≥70%). In tissues, the conjugated-GalNAc sugar moiety was rapidly metabolized, leaving the fully unconjugated form as the only full-length oligonucleotide detected at 48 h after dosing. Unconjugated ISIS 681257 cleared slowly from tissues with a half-life of 4 weeks. ISIS 681257 was highly bound to plasma proteins (>97% bound), which limited its urinary excretion. Disposition of ISIS 681257 in plasma and liver appeared nonlinear over the 1-40 mg/kg dose range studied. The plasma and liver tissue concentration data were well described by a population based mixed-effects modeling approach with Michaelis-Menten uptake from plasma to liver. Safety data from the study and the good exposure, as well as the extended half-life of the unconjugated ASO in the liver, support further development and less frequent dosing in Phase I clinical study.

Disposition and Pharmacology of a GalNAc3-conjugated ASO Targeting Human Lipoprotein (a) in Mice.

Triantennary N-acetyl galactosamine (GalNAc3)-conjugated antisense oligonucleotides (ASOs) have greatly improved potency via receptor-mediated uptake. In the present study, the in vivo pharmacology of a 2'-O-(2-methoxyethyl)-modified ASO conjugated with GalNAc3 (ISIS 681257) together with its unmodified congener (ISIS 494372) targeting human apolipoprotein (a) (apo(a)), were studied in human LPA transgenic mice. Further, the disposition kinetics of ISIS 681257 was studied in CD-1 mice. ISIS 681257 demonstrated over 20-fold improvement in potency over ISIS 494372 as measured by liver apo(a) mRNA and plasma apo(a) protein levels. Following subcutaneous (SC) dosing, ISIS 681257 cleared rapidly from plasma and distributed to tissues. Intact ISIS 681257 was the major full-length oligonucleotide species in plasma. In tissues, however, GalNAc sugar moiety was rapidly metabolized and unconjugated ISIS 681257 accounted > 97% of the total exposure, which was then cleared slowly from tissues with a half-life of 7-8 days, similar to the half-life in plasma. ISIS 681257 is highly bound to plasma proteins (> 94% bound), which limited its urinary excretion. This study confirmed dose-dependent exposure to the parent drug ISIS 681257 in plasma and rapid conversion to unconjugated ASO in tissues. Safety data and the extended half-life support its further development and weekly dosing in phase 1 clinical studies.

Elucidation of the Biotransformation Pathways of a Galnac3-conjugated Antisense Oligonucleotide in Rats and Monkeys.

Triantennary N-acetyl galactosamine (GalNAc3) is a high-affinity ligand for hepatocyte-specific asialoglycoprotein receptors. Conjugation with GalNAc3 via a trishexylamino (THA)-C6 cluster significantly enhances antisense oligonucleotide (ASO) potency. Herein, the biotransformation, disposition, and elimination of the THA cluster of ION-681257, a GalNAc3-conjugated ASO currently in clinical development, are investigated in rats and monkey. Rats were administered a single subcutaneous dose of (3)H-radiolabeled ((3)H placed in THA) or nonradiolabeled ION-681257. Mass balance included radiometric profiling and metabolite fractionation with characterization by mass spectrometry. GalNAc3-conjugated ASOs were extensively distributed into liver. The THA-C6 triantenerrary GalNAc3 conjugate at the 5'-end of the ASO was rapidly metabolized and excreted with 25.67 ± 1.635% and 71.66 ± 4.17% of radioactivity recovered in urine and feces within 48 hours postdose. Unchanged drug, short-mer ASOs, and linker metabolites were detected in urine. Collectively, 14 novel linker associated metabolites were discovered including oxidation at each branching arm, initially by monooxidation at the ß-position followed by dioxidation at the α-arm, and lastly, tri and tetra oxidations on the two remaining ß-arms. Metabolites in bile and feces were identical to urine except for oxidized linear and cyclic linker metabolites. Enzymatic reaction phenotyping confirmed involvement of N-acetyl-ß-glucosaminidase, deoxyribonuclease II, alkaline phosphatase, and alcohol + aldehyde dehydrogenases on the complex metabolism pathway for THA supplementing in vivo findings. Lastly, excreta from monkeys treated with ION-681257 revealed the identical series as observed in rat. In summary, our findings provide an improved understanding of GalNAc3-conjugated-ASO metabolism pathways which facilitate similar development programs.

Pharmacokinetic and Pharmacodynamic Investigations of ION-353382, a Model Antisense Oligonucleotide: Using Alpha-2-Macroglobulin and Murinoglobulin Double-Knockout Mice.

To investigate the pharmacokinetics (PKs) and pharmacodynamics (PDs) for ION-353382, an antisense oligonucleotide (ASO) targeting scavenger receptor class B type I (SRB1) mRNA, using alpha-2-macroglobulin (A2M), murinoglobulin double-knockout (DKO), and wild-type mice. Wild-type and DKO homozygous mice were administered a single subcutaneous injection of ION-353382 at 0, 5, 15, 30, and 60 mg/kg. Mice were sacrificed at 72 h with plasma and organs harvested. Both liquid chromatography-mass spectrometry (LC-MS) and enzyme-linked immunosorbent assay (ELISA) were used to determine ASO exposure with real-time PCR for SRB1 expression. Immunohistochemistry was evaluated to explore hepatic uptake of ASOs. The total plasma protein binding and profiling was assessed. Finally, two-dimensional gel electrophoresis identified protein expression differences. PK exposures were comparable between wild-type and DKO mice in plasma, liver, and kidney, yet a near twofold reduction in EC50 was revealed for DKO mice based on an inhibitory effect liver exposure response model. Total plasma protein binding and profiling revealed no major dissimilarities between both groups. Plasma proteome fingerprinting confirmed protein expression variations related to A2M. Histological examination revealed enhanced ASO distribution into hepatocytes and less nonparenchymal uptake for DKO mice compared to wild-type mice. Knocking out A2M showed improved PD activities without an effect on total plasma and tissue exposure kinetics. Binding to A2M could mediate ASOs to nonproductive compartments, and thus, decreased binding of ASOs to A2M could potentially improve ASO pharmacology.

Lack of Interactions Between an Antisense Oligonucleotide with 2'-O-(2-Methoxyethyl) Modifications and Major Drug Transporters.

ISIS 141923 is a model compound of 2'-O-(2-methoxyethyl) (2'-MOE) modified antisense oligonucleotides (ASOs). The purpose of this study is to determine whether ISIS 141923 is a substrate or an inhibitor against a panel of nine major uptake or efflux drug transporters, namely breast cancer resistance protein (BCRP), P-glycoprotein (P-gp), organic anion transporter (OAT)1, OAT3, organic cation transporter (OCT)1, OCT2, organic anion transporting polypeptide 1B (OATP1B)1, OATP1B3, and bile salt export pump (BSEP), in vitro. The uptake test system for transporters in the solute carrier (SLC) family (OAT1, OAT3, OCT1, OCT2, OATP1B1, and OATP1B3) was studied in Madin-Darby canine kidney (MDCK)-II cells transfected to express the transporters of interest. BCRP was studied using carcinoma colon-2 (Caco-2) cells with endogenously expressed BCRP. P-gp transporter was studied in MDCK-multi-drug resistance 1 (MDR1) cells, while BSEP was studied using Spodoptera frugiperda 9 (Sf9) membrane vesicles containing human BSEP. The ISIS 141293 concentrations evaluated were 10 and 100 µM for the substrate and inhibition study, respectively. Cellular uptake of ISIS 141923 was analyzed using a high performance liquid chromatography-mass spectrometry method, while concentrations of known substrates (used as positive controls) of each transporters evaluated were determined by radiometric detection. At 10 µM ISIS 141923, there was no significant transporter-mediated uptake of ISIS 141923 (P > 0.05) in the SLC family, and the efflux ratios were not above 2.0 for either BCRP or P-gp. Therefore, no transporter-mediated uptake of ISIS 141923 was observed by any of the nine transporters studied. At 100 µM ISIS 141923, the % inhibition was in the range of -16.0% to 19.0% for the nine transporters evaluated. Therefore, ISIS 141923 is not considered as an inhibitor of the nine transporters studied. Overall, the results from this study suggest that it is unlikely that ISIS 141923 or similar 2'-MOE ASOs would interact with small molecule drugs either as a victim (substrate) or perpetrator (inhibitor) of major transporters in humans. The results from available clinical drug-drug interaction studies conducted with this class of compounds to date are also supportive of this conclusion.