A First-in-Human Phase 1 Study of a Tumor-Directed RNA-Interference Drug against HIF2α in Patients with Advanced Clear Cell Renal Cell Carcinoma

PURPOSE

ARO-HIF2 is an siRNA drug designed to selectively target hypoxia-inducible factor-2α (HIF2α) interrupting downstream pro-oncogenic signaling in clear cell renal cell carcinoma (ccRCC). The aims of this Phase 1 study (AROHIF21001) were to evaluate safety, tolerability, pharmacokinetics, and establish a recommended Phase 2 dose.

PATIENTS AND METHODS

Subjects with ccRCC and progressive disease after at least 2 prior therapies that included VEGF and immune checkpoint inhibitors were progressively enrolled into dose-escalation cohorts of ARO-HIF2 administered intravenously at 225, 525, or 1,050 mg weekly.

RESULTS

Twenty-six subjects received ARO-HIF2. The most common treatment emergent adverse events (AE) irrespective of causality were fatigue (50.0%), dizziness (26.9%), dyspnea (23.1%), and nausea (23.1%). Four subjects (15.4%) had treatment-related serious AEs. AEs of special interest included neuropathy, hypoxia, and dyspnea. ARO-HIF2 was almost completely cleared from plasma circulation within 48 hours with minimal renal clearance. Reductions in HIF2α were observed between pre- and post-dosing tumor biopsies, but the magnitude was quite variable. The objective response rate was 7.7% and the disease control rate was 38.5%. Responses were accompanied by ARO-HIF2 uptake in tumor cells, HIF2α downregulation, as well as rapid suppression of tumor produced erythropoietin (EPO) in a patient with paraneoplastic polycythemia.

CONCLUSIONS

ARO-HIF2 downregulated HIF2α in advanced ccRCC-inhibiting tumor growth in a subset of subjects. Further development was hampered by off-target neurotoxicity and low response rate. This study provides proof of concept that siRNA can target tumors in a specific manner.

HIF2 Inactivation and Tumor Suppression with a Tumor-Directed RNA-Silencing Drug in Mice and Humans

PURPOSE

HIF2α is a key driver of kidney cancer. Using a belzutifan analogue (PT2399), we previously showed in tumorgrafts (TG) that ∼50% of clear cell renal cell carcinomas (ccRCC) are HIF2α dependent. However, prolonged treatment induced resistance mutations, which we also identified in humans. Here, we evaluated a tumor-directed, systemically delivered, siRNA drug (siHIF2) active against wild-type and resistant-mutant HIF2α.

EXPERIMENTAL DESIGN

Using our credentialed TG platform, we performed pharmacokinetic and pharmacodynamic analyses evaluating uptake, HIF2α silencing, target gene inactivation, and antitumor activity. Orthogonal RNA-sequencing studies of siHIF2 and PT2399 were pursued to define the HIF2 transcriptome. Analyses were extended to a TG line generated from a study biopsy of a siHIF2 phase I clinical trial (NCT04169711) participant and the corresponding patient, an extensively pretreated individual with rapidly progressive ccRCC and paraneoplastic polycythemia likely evidencing a HIF2 dependency.

RESULTS

siHIF2 was taken up by ccRCC TGs, effectively depleted HIF2α, deactivated orthogonally defined effector pathways (including Myc and novel E2F pathways), downregulated cell cycle genes, and inhibited tumor growth. Effects on the study subject TG mimicked those in the patient, where HIF2α was silenced in tumor biopsies, circulating erythropoietin was downregulated, polycythemia was suppressed, and a partial response was induced.

CONCLUSIONS

To our knowledge, this is the first example of functional inactivation of an oncoprotein and tumor suppression with a systemic, tumor-directed, RNA-silencing drug. These studies provide a proof-of-principle of HIF2α inhibition by RNA-targeting drugs in ccRCC and establish a paradigm for tumor-directed RNA-based therapeutics in cancer.

Combination treatments including the small-interfering RNA JNJ-3989 induce rapid and sometimes prolonged viral responses in patients with CHB

BACKGROUND & AIMS

RNA interference therapy has been shown to reduce hepatitis B surface antigen (HBsAg) levels in preclinical models, which could confer functional cure in patients with chronic hepatitis B. This phase IIa trial (ClinicalTrials.gov Identifier: NCT03365947) assessed the safety and efficacy of the small-interfering RNA JNJ-73763989 (JNJ-3989) plus a nucleos(t)ide analogue (NA), with/without the capsid assembly modulator JNJ-56136379 (JNJ-6379) in patients with chronic hepatitis B.

METHODS

Treatment-naïve and NA-suppressed patients received 3 subcutaneous JNJ-3989 doses every week (QW; 100, 200, or 300 mg), 2 weeks (Q2W; 100 mg) or 4 weeks (Q4W; 25, 50, 100, 200, 300, or 400 mg), or JNJ-3989 Q4W (200 mg) plus oral JNJ-6379 250 mg daily for 12 weeks. Patients received NAs throughout.

RESULTS

Eighty-four patients were recruited. All treatments were well tolerated, with all 5 serious adverse events considered unrelated to study drugs. JNJ-3989 100 to 400 mg Q4W resulted in HBsAg reductions ≥1 log₁₀ IU/ml from baseline in 39/40 (97.5%) patients at the nadir. All patients receiving the triple combination (n = 12) had HBsAg reductions ≥1 log₁₀ IU/ml from baseline at the nadir. HBsAg reductions were similar for HBeAg-positive (n = 21) and HBeAg-negative (n = 47) patients in all JNJ-3989 Q4W treatment arms, including the triple combination (n = 68). Smaller HBsAg reductions were seen with 25 mg (n = 8) and 50 mg (n = 8) than with 100 to 400 mg (n = 40). Shorter dosing intervals (QW [n = 12] and Q2W [n = 4]) did not improve response vs. Q4W dosing. HBsAg reductions ≥1 log₁₀ IU/ml from baseline persisted in 38% of patients 336 days after the last JNJ-3989 dose.

CONCLUSIONS

JNJ-3989 plus an NA, with/without JNJ-6379, was well tolerated and resulted in HBsAg reductions up to 336 days after the last JNJ-3989 Q4W dose.

CLINICAL TRIAL NUMBER

NCT03365947.

LAY SUMMARY

Hepatitis B virus affects people's livers and produces particles called hepatitis B surface antigen (HBsAg) that damage a person's liver and can help the virus infect a person for a long time, known as chronic hepatitis B (CHB). In this study, a new treatment called JNJ-3989 was assessed (in combination with normal treatment known as nucleos(t)ide analogues), for its safety and effectiveness in reducing the number of HBsAg particles in people with CHB. The results of this study showed that treatment with JNJ-3989 could be safe for people with CHB, lowered their HBsAg levels, and kept HBsAg levels lowered for 336 days in 38% of patients after receiving their last dose of JNJ-3989.

Fazirsiran for Liver Disease Associated with Alpha1-Antitrypsin Deficiency

BACKGROUND

Alpha₁-antitrypsin (AAT) deficiency results from carriage of a homozygous SERPINA1 "Z" mutation (proteinase inhibitor [PI] ZZ). The Z allele produces a mutant AAT protein called Z-AAT, which accumulates in hepatocytes and can lead to progressive liver disease and fibrosis. This open-label, phase 2 trial investigated the safety and efficacy of fazirsiran, an RNA interference therapeutic, in patients with liver disease associated with AAT deficiency.

METHODS

We assigned adults with the PI ZZ genotype and liver fibrosis to receive fazirsiran at a dose of 200 mg (cohorts 1 [4 patients] and 2 [8 patients]) or 100 mg (cohort 1b [4 patients]) subcutaneously on day 1 and week 4 and then every 12 weeks. The primary end point was the change from baseline to week 24 (cohorts 1 and 1b) or week 48 (cohort 2) in liver Z-AAT concentrations, which were measured by means of liquid chromatography-mass spectrometry.

RESULTS

All the patients had reduced accumulation of Z-AAT in the liver (median reduction, 83% at week 24 or 48). The nadir in serum was a reduction of approximately 90%, and treatment was also associated with a reduction in histologic globule burden (from a mean score of 7.4 [scores range from 0 to 9, with higher scores indicating a greater globule burden] at baseline to 2.3 at week 24 or 48). All cohorts had reductions in liver enzyme concentrations. Fibrosis regression was observed in 7 of 15 patients and fibrosis progression in 2 of 15 patients after 24 or 48 weeks. There were no adverse events leading to trial or drug discontinuation. Four serious adverse events (viral myocarditis, diverticulitis, dyspnea, and vestibular neuronitis) resolved.

CONCLUSIONS

In this small trial, fazirsiran was associated with a strong reduction of Z-AAT concentrations in the serum and liver and concurrent improvements in liver enzyme concentrations. (Funded by Arrowhead Pharmaceuticals; AROAAT-2002 ClinicalTrials.gov number, NCT03946449.).

Abstract 6304: Targeting HIF2a with siRNA: From preclinical models to the clinic

Hypoxia-inducible factor 2 alpha (HIF2a) is arguably the most important driver of kidney cancer. HIF2a is constitutively activated following von Hippel-Lindau (VHL) gene inactivation, the signature event of the most common type of kidney cancer, clear cell renal cell carcinoma (ccRCC). HIF2a functions as a heterodimeric transcription factor and regulates a program of gene expression that promotes cell proliferation, stemness, and angiogenesis. Using a highly specific inhibitor designed to target a structural vulnerability in HIF2a (PT2399), we previously showed that approximately 50% of ccRCCs are dependent on HIF2a. However, prolonged drug exposure results in resistance and the acquisition of gatekeeper mutations, which we reported first in patient-derived xenografts (PDXs) and subsequently in humans. Using the same PDX platform that previously validated PT2399, we show that HIF2a can be effectively inhibited using a tumor-directed siRNA (siHIF2). Referring herein to both first- and second-generation (ARO-HIF2) siRNA drugs, siHIF2 is specifically taken up by human ccRCC tumors transplanted in mice, where it depletes HIF2a inhibiting target gene expression and tumor growth. Through orthogonal RNA-seq studies integrating both PT2399 and siHIF2 in PDXs, we provide unprecedented detail on the HIF2a effector transcriptome, which we further dissect by incorporating ChIP-seq. A PDX line was generated from a ccRCC patient who had paraneoplastic polycythemia (a HIF2a dependent syndrome due to erythropoietin [Epo] secretion by the tumor) and participated in the phase I trial of ARO-HIF2 (NCT04169711). We show that siHIF2 effectively depleted HIF2a in both the PDX as well as in the patient, that it normalized Epo (and hemoglobin), and that it inhibited tumor growth. siHIF2 has activity against both wild-type and drug-resistant mutant HIF2a and is expected to be active in patients progressing on PT2977 (belzutifan), a PT2399-related drug recently approved by the FDA. To our knowledge, this is the first example of functional inactivation of an oncoprotein with a tumor-directed siRNA in humans. In summary, these studies provide unique insight into HIF2a (the only known core dependency in ccRCC), illustrate how it can be effectively inhibited by an siRNA drug, and establish a paradigm for the development of tumor directed siRNA-based therapeutics.

Citation Format: Yuanqing Ma, Christina Stevens, Olivia Brandenburg, Vanina Toffessi Tcheuyap, Quyen N. Do, Faeze Saatchi, Tanner Hardy, Oluwatomilade Fatunde, Alyssa Macchiaroli, Jeffrey Miyata, Deyssy Carrillo, Thomas Schluep, So Wong, Alana Christie, Payal Kapur, Ivan Pedrosa, James Hamilton, James Brugarolas. Targeting HIF2a with siRNA: From preclinical models to the clinic [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 6304.

JNJ-73763989 pharmacokinetics and safety: Liver-targeted siRNAs against hepatitis B virus, in Japanese and non-Japanese healthy adults, and combined with JNJ-56136379 and a nucleos(t)ide analogue in patients with chronic hepatitis B

BACKGROUND

JNJ-73763989 comprises two hepatitis B virus (HBV)-specific, liver-targeted N-galactosamine-conjugated short interfering RNA triggers, JNJ-73763976 and JNJ-73763924. JNJ-73763989 pharmacokinetics, safety and tolerability were assessed in two phase 1 studies: Japanese (NCT04002752), and non-Japanese healthy participants and chronic hepatitis B (CHB) patients also receiving the HBV capsid assembly modulator JNJ-56136379 and a nucleos(t)ide analogue (NA) (NCT03365947).

METHODS

Healthy participant cohorts were double-blind and randomized to receive a single subcutaneous JNJ-73763989 dose (non-Japanese participants, 35, 100, 200, 300 or 400 mg; Japanese participants, 25, 100 or 200 mg) or placebo. JNJ-73763976 and JNJ-73763924 plasma concentrations were assessed over 48 h. CHB patients received JNJ-73763989 200 mg every 4 weeks plus daily oral JNJ-56136379 250 mg and NA in an open-label fashion. Safety and tolerability were assessed through Day 28 (healthy participants) or Day 112 (patients).

RESULTS

Thirty non-Japanese (n = 4/dose; placebo, n = 10) and 24 Japanese healthy participants (n = 6/dose; placebo, n = 6) were randomized. JNJ-73763976 and JNJ-73763924 exposure generally increased in a dose-proportional manner. Mean plasma half-life was 4-9 h. No differences between pharmacokinetic parameters were apparent between non-Japanese and Japanese healthy participants. In the 12 CHB patients, mean JNJ-73763976, JNJ-73763924 and JNJ-56136379 plasma concentrations 2 h post-dose on Day 29 were 663, 269 and 14,718 ng/mL, respectively. In both studies, all adverse events were mild/moderate.

CONCLUSION

JNJ-73763976 and JNJ-73763924 had short plasma half-lives and exposure generally increased in a dose-proportional manner; there were no pharmacokinetic differences between Japanese and non-Japanese healthy adults. JNJ-73763989 with or without JNJ-56136379 and NA was generally safe and well tolerated.

Long-term serological, virological and histological responses to RNA inhibition by ARC-520 in Chinese chronic hepatitis B patients on entecavir treatment

OBJECTIVE

We examined the serological, virological (in serum and liver) and histological profiles in chronic hepatitis B virus (HBV) patients during and after completion of multiple dose (MD) ARC-520.

DESIGN

The present phase 1b study was a multidose, open-label extension cohort of patients that had received single dose ARC-520 in our previous study. Eight patients received 4-9 4 weekly doses of MD ARC-520 and entecavir. Liver biopsies were performed in six patients. Intrahepatic and serum HBV DNA, HBV RNA and viral antigens were measured.

RESULTS

All patients had 28.9-30.4 months of follow-up after the last MD. All three hepatitis B e antigen (HBeAg)-positive patients had profound reductions in hepatitis B surface antigen (HBsAg), HBeAg, hepatitis B core-related antigen and HBV RNA with two undergoing HBeAg seroconversion. One further achieved HBsAg seroconversion (anti-HBs level of 25.1 IU/L) and the remaining two had HBsAg reductions of -1.7 and -3.5 log IU/mL >30 months after MD. Among the five HBeAg-negative patients, four had modest HBsAg reduction >29 months after completion of MD and one achieved HBsAg seroconversion (anti-HBs level of 152.5 IU/L) and was negative for liver HBsAg staining. Entecavir was successfully stopped in this patient 12 months after HBsAg seroconversion. Temporally related alanine aminotransferase elevations preceded by HBsAg reductions were observed in three patients suggesting immune activation. HBcAg staining was negative in all six biopsied patients. Two patients with <10% HBsAg positive staining of hepatocytes had correspondingly low serum HBsAg levels of 1.5 and 11.5 IU/mL.

CONCLUSIONS

MD ARC-520 therapy achieved sustained and profound reductions of viral antigens and HBV RNA. HBsAg seroclearance was achievable.

TRIAL REGISTRATION NUMBER

NCT02065336.

Initial results from the phase 1 study of ARO-HIF2 to silence HIF2-alpha in patients with advanced ccRCC (AROHIF21001)

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Background: Hypoxia inducible factor-2 alpha (HIF2a) is a transcription factor and key tumorigenic driver of clear cell renal cell carcinoma (ccRCC). Normally, HIF2a is expressed at low levels and targeted for degradation by the von Hippel-Lindau ( VHL) tumor suppressor protein. VHL inactivation, the causative event of ccRCC, induces tumorigenesis through uncontrolled accumulation of HIF2a and constitutive expression of downstream target genes implicated in cell survival, cell proliferation and angiogenesis. ARO-HIF2 is a synthetic double-stranded RNAi trigger with an alpha-v beta3 targeting ligand, designed to silence HIF2a expression. Herein, we present initial results from a phase 1 clinical trial of ARO-HIF2 in advanced ccRCC (NCT04169711). Methods: Advanced ccRCC patients (pts) (ECOG ≤ 1), with progressive disease on prior anti-VEGF and checkpoint inhibitor therapy, were enrolled into three escalating dose cohorts (up to 10 per cohort) to receive 225, 525 or 1,050 mg i.v. weekly of ARO-HIF2 until progression or unacceptable toxicity. The primary endpoint was incidence and severity of AEs. Secondary endpoints included tumor response based on RECIST. All pts underwent tumor biopsy at baseline and post-dose for analysis of changes in HIF2a mRNA (qPCR) and protein expression (IHC). Results: At the time of data cut, twenty-three pts (median age 66.5) were enrolled across 3 cohorts. Seventy four percent of pts received ≥ 3 prior lines of therapy. The most common treatment emergent AE was fatigue (39%). Three SAEs in 3 pts were reported by investigators as possibly drug related including, myocarditis (in a pt with a history of TKI induced cardiomyopathy and NSTEMI requiring stent placement), demyelinating neuropathy (in a pt with autoimmune sequelae secondary to checkpoint inhibitors), and hypoxia (in a pt with a pulmonary infiltrate treated with antibiotics). No cases of drug related anemia were reported. Among pts with adequate biopsy for qPCR (n=7), mean (max) reductions in HIF2a mRNA were 38% (47%), 25% (30%) and 28% (28%) in cohorts 1, 2, and 3, respectively. Among pts with adequate biopsy for IHC (n = 12), 8 showed reductions in HIF2a protein with mean (max) reductions of 45% (82%), 57% (90%) and 63% (63%) in cohorts 1, 2, 3, respectively. Across all 3 cohorts, disease control (CR+PR+SD) was seen in 7 (30%) of pts. One pt (cohort 2, with prior sunitinib, nivolumab, axitinib) experienced a partial response with 66% reduction in sum of longest diameters. Six pts had a best response of stable disease. Three pts remain on drug with stable disease and treatment durations between 20 and 32 weeks. Conclusions: HIF2a is a clinically validated driver of ccRCC which can be targeted with a RNAi therapeutic. This ongoing phase 1 study provides initial proof of target engagement based on reductions in HIF2a expression as well as a favorable safety profile in response to escalating doses of ARO-HIF2. Clinical trial information: NCT04169711.

RNA Interference Therapy With ARC-520 Results in Prolonged Hepatitis B Surface Antigen Response in Patients With Chronic Hepatitis B Infection

BACKGROUND AND AIMS

ARC-520, the first an RNA interference (RNAi) therapeutic, was designed to reduce all RNA transcripts derived from covalently closed circular DNA, leading to a reduction in viral antigens and hepatitis B virus (HBV) DNA.

APPROACH AND RESULTS

We aimed to evaluate the depth of hepatitis B surface antigen (HBsAg) decline in response to multiple doses of ARC-520 compared to placebo (PBO) in two randomized, multicenter studies in nucleoside/nucleotide analogue reverse-transcriptase inhibitor (NUC)-experienced patients with hepatitis B early antigen (HBeAg)-negative (E-neg) or HBeAg-positive (E-pos) disease. A total of 58 E-neg and 32 E-pos patients were enrolled and received four monthly doses of PBO (n = 20 E-neg, 11 E-pos), 1 mg/kg ARC-520 (n = 17 E-neg, 10 E-pos), or 2 mg/kg ARC-520 (n = 21 E-neg, 11 E-pos) concomitantly with NUC. HBsAg change from baseline to 30 days after the last ARC-520 dose were compared to PBO. Both E-neg and E-pos high-dose groups significantly reduced HBsAg compared to PBO, with mean reductions of 0.38 and 0.54 log IU/mL, respectively. HBsAg reductions persisted for approximately 85 days and >85 days after the last dose in E-neg and E-pos patients, respectively. The low-dose groups did not reach statistical significance in either study. E-pos patients showed a dose-dependent reduction in HBeAg from baseline. Mean maximum reduction was 0.23 and 0.69 log Paul Ehrlich IUs/mL in the low-dose and high dose ARC-520 groups respectively. ARC-520 was well tolerated, with only two serious adverse events of pyrexia possibly related to study drug observed.

CONCLUSIONS

ARC-520 was active in both E-neg and E-pos, NUC-experienced HBV patients; but absolute HBsAg reductions were moderate, possibly due to expression of HBsAg from integrated HBV DNA, indicating the need for RNAi therapeutics that can target viral transcripts regardless of origin.

RNAi-based treatment of chronically infected patients and chimpanzees reveals that integrated hepatitis B virus DNA is a source of HBsAg

Chronic hepatitis B virus (HBV) infection is a major health concern worldwide, frequently leading to liver cirrhosis, liver failure, and hepatocellular carcinoma. Evidence suggests that high viral antigen load may play a role in chronicity. Production of viral proteins is thought to depend on transcription of viral covalently closed circular DNA (cccDNA). In a human clinical trial with an RNA interference (RNAi)-based therapeutic targeting HBV transcripts, ARC-520, HBV S antigen (HBsAg) was strongly reduced in treatment-naïve patients positive for HBV e antigen (HBeAg) but was reduced significantly less in patients who were HBeAg-negative or had received long-term therapy with nucleos(t)ide viral replication inhibitors (NUCs). HBeAg positivity is associated with greater disease risk that may be moderately reduced upon HBeAg loss. The molecular basis for this unexpected differential response was investigated in chimpanzees chronically infected with HBV. Several lines of evidence demonstrated that HBsAg was expressed not only from the episomal cccDNA minichromosome but also from transcripts arising from HBV DNA integrated into the host genome, which was the dominant source in HBeAg-negative chimpanzees. Many of the integrants detected in chimpanzees lacked target sites for the small interfering RNAs in ARC-520, explaining the reduced response in HBeAg-negative chimpanzees and, by extension, in HBeAg-negative patients. Our results uncover a heretofore underrecognized source of HBsAg that may represent a strategy adopted by HBV to maintain chronicity in the presence of host immunosurveillance. These results could alter trial design and endpoint expectations of new therapies for chronic HBV.

Safety, Tolerability, and Pharmacokinetics of ARC-520 Injection, an RNA Interference-Based Therapeutic for the Treatment of Chronic Hepatitis B Virus Infection, in Healthy Volunteers

ARC‐520 Injection, an RNA interference drug for the treatment of hepatitis B that targets cccDNA‐derived viral mRNA transcripts with high specificity, effectively reduces the production of viral proteins and HBV DNA. In this phase 1 randomized, double‐blind, placebo‐controlled study, 54 healthy volunteers (half male, half female) received a single, intravenous dose of 0.01–4.0 mg/kg ARC‐520 Injection (n = 36) or placebo (n = 18). Assessments included safety, tolerability, pharmacokinetics, and pharmacodynamics (cytokines and complement). Pharmacokinetics of the siRNA and peptide excipient components contained in ARC‐520 Injection showed a relatively short half‐life of 3–5 and 8–10 hours, respectively. Dose exposure linearity was demonstrated within the dose range. ARC‐520 Injection was well tolerated, with adverse‐event frequency the same as placebo and no serious adverse events. ARC‐520 Injection was initially found to induce histamine release through mast cell degranulation, resulting in 2 moderate hypersensitivity reactions. However, after initiation of pretreatment with oral antihistamine, no further hypersensitivity reactions occurred. Low‐level, transient complement induction and sporadic, mild, and transient elevations of several cytokines were observed but not associated with any symptoms. ARC‐520 Injection showed a favorable tolerability profile in this single‐dose study in healthy volunteers. Oral antihistamine pretreatment is recommended in the future to offset mast cell degranulation stimulation.

Synthetic RNAi triggers and their use in chronic hepatitis B therapies with curative intent

Current therapies for chronic hepatitis B virus infection (CHB) - nucleos(t)ide analogue reverse transcriptase inhibitors and interferons - result in low rates of functional cure defined as sustained off-therapy seroclearance of hepatitis B surface antigen (HBsAg). One likely reason is the inability of these therapies to consistently and substantially reduce the levels of viral antigen production. Accumulated evidence suggests that high serum levels of HBsAg result in exhaustion of the host immune system, rendering it unable to mount the effective antiviral response required for HBsAg clearance. New mechanistic approaches are required to produce high rates of HBsAg seroclearance in order to greatly reduce off-treatment disease progression. Already shown to be a clinically viable means of reducing gene expression in a number of other diseases, therapies based on RNA interference (RNAi) can directly target hepatitis B virus transcripts with high specificity, profoundly reducing the production of viral proteins. The fact that the viral RNA transcripts contain overlapping sequences means that a single RNAi trigger can result in the degradation of all viral transcripts, including all messenger RNAs and pregenomic RNA. Advances in the design of RNAi triggers have increased resistance to degradation and reduced nonspecific innate immune stimulation. Additionally, new methods to effectively deliver the trigger to liver hepatocytes, and specifically to the cytoplasmic compartment, have resulted in increased efficacy and tolerability. An RNAi-based drug currently in clinical trials is ARC-520, a dynamic polyconjugate in which the RNAi trigger is conjugated to cholesterol, which is coinjected with a hepatocyte-targeted, membrane-active peptide. Phase 2a clinical trial results indicate that ARC-520 was well tolerated and resulted in significant, dose-dependent reduction in HBsAg for up to 57days in CHB patients. RNAi-based therapies may play an important role in future therapeutic regimes aimed at improving HBsAg seroclearance and eliminating the need for lifelong therapy. This paper forms part of a symposium in Antiviral Research on "An unfinished story: from the discovery of the Australia antigen to the development of new curative therapies for hepatitis B."

Chronic hepatitis B: Virology, natural history, current management and a glimpse at future opportunities

The host immune system plays an important role in chronic hepatitis B (CHB), both in viral clearance and hepatocellular damage. Advances in our understanding of the natural history of the disease have led to redefining the major phases of infection, with the "high replicative, low inflammatory" phase now replacing what was formerly termed the "immune tolerant" phase, and the "nonreplicative phase" replacing what was formerly termed the "inactive carrier" phase. As opposed to the earlier view that HBV establishes chronic infection by exploiting the immaturity of the neonate's immune system, new findings on trained immunity show that the host is already somewhat "matured" following birth, and is actually very capable of responding immunologically, potentially altering future hepatitis B treatment strategies. While existing therapies are effective in reducing viral load and necroinflammation, often restoring the patient to near-normal health, they do not lead to a cure except in very rare cases and, in many patients, viremia rebounds after cessation of treatment. Researchers are now challenged to devise therapies that will eliminate infection, with a particular focus on eliminating the persistence of viral cccDNA in the nuclei of hepatocytes. In the context of chronic hepatitis B, new definitions of 'cure' are emerging, such as 'functional' and 'virological' cure, defined by stable off-therapy suppression of viremia and antigenemia, and the normalization of serum ALT and other liver-related laboratory tests. Continued advances in the understanding of the complex biology of chronic hepatitis B have resulted in the development of new, experimental therapies targeting viral and host factors and pathways previously not accessible to therapy, approaches which may lead to virological cures in the near term and functional cures upon long term follow-up. This article forms part of a symposium in Antiviral Research on "An unfinished story: from the discovery of the Australia antigen to the development of new curative therapies for hepatitis B."

Abstract LB-94: Nanoparticle-based RNAi therapy for the delivery of personalized siRNA payloads to KRAS-driven tumors

The current landscape of druggable disease targets represents only ~10% of the human genome. Among those targets that are frequently mutated in cancer yet remain undruggable by conventional small molecules are the Ras family of GTPases. Somatic mutations in KRAS occur in 35% of colorectal cancers, 16% of lung cancers and 61% of pancreatic cancers. Common KRAS mutations lock the enzyme in the active GTP-bound state, which leads to constitutive activation of downstream effector modules such as MAPK, PI3K, Ral, Rac and Rho, which promote tumor growth, proliferation and survival.

RNAi interference allows for the ablation of any gene product through the engagement of the endogenous microRNA machinery. The successful delivery of siRNA against KRAS or downstream effectors to tumors would represent a novel alternative treatment for KRASmut cancers, which currently lack strong clinical options. We have thus developed an RNAi therapy that employs 1) a cyclodextrin-based nanoparticle with high siRNA carrying capacity and tumor-targeting modules; and 2) highly potent “Sensor” siRNAs that can be used at low dose to efficiently ablate gene targets while avoiding off-target effects.

We have assembled a library of potent Sensor siRNAs, which are identified using a massively parallel biological assay. These siRNA sequences are screened in high-throughput in KRASmut cell lines for negative effects on viability and disruption of cellular signaling pathways (ViBE, Bioscale). To subsequently assess the ability of these personalized nanoparticle-siRNA treatments to inhibit the growth of KRASmut tumors, we have developed an in vivo screening platform to monitor nanoparticle-siRNA delivery and payload efficacy at varying siRNA doses. Successful delivery of siRNAs to solid tumors has been one of the major hurdles to the advancement of RNAi therapy. Our fluorescent reporter system thus allows for the careful tracking of nanoparticle delivery and siRNA payload activity in real time using optical imaging. Additionally, the effect of different nanoparticle-siRNA treatments on transduced tumor cells can be measured non-invasively in real time.

We demonstrate that delivery of low dose Sensor siRNAs targeting KRAS and other effector genes to KRASmut xenograft tumors significantly impedes tumor growth by inhibition of MAPK signaling and induction of apoptosis. The highly customizable nature of the siRNA payload offers a promising and universal platform to access previously intractable targets such as KRAS and personalize treatment for various oncogene-addicted tumors.

Citation Format: Tina L. Yuan, Chih-Shia Lee, Christof Fellmann, Cayde Ritchie, Changwoo Lee, Colin Merrifield, Thomas Schluep, Scott W. Lowe, Ji Luo, Frank McCormick. Nanoparticle-based RNAi therapy for the delivery of personalized siRNA payloads to KRAS-driven tumors. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr LB-94. doi:10.1158/1538-7445.AM2013-LB-94

CRLX101 (formerly IT-101)-A Novel Nanopharmaceutical of Camptothecin in Clinical Development

CRLX101 (formerly IT-101) is a first-in-class nanopharmaceutical, currently in Phase 2a development, which has been developed by covalently conjugating camptothecin (CPT) to a linear, cyclodextrin-polyethylene glycol (CD-PEG) co-polymer that self-assembles into nanoparticles. As a nanometer-scale drug carrier system, the cyclodextrin polymeric nanoparticle technology, referred to as “CDP”, has unique design features and capabilities. Specifically, CRLX101 preclinical and clinical data confirm that CDP can address not only solubility, formulation, toxicity, and pharmacokinetic challenges associated with administration of CPT, but more importantly, can impart unique biological properties that enhance CPT pharmacodynamics and efficacy.

Preclinical results of camptothecin-polymer conjugate (IT-101) in multiple human lymphoma xenograft models

PURPOSE

Camptothecin (CPT) has potent broad-spectrum antitumor activity by inhibiting type I DNA topoisomerase (DNA topo I). It has not been used clinically because it is water-insoluble and highly toxic. As a result, irinotecan (CPT-11), a water-soluble analogue of CPT, has been developed and used as salvage chemotherapy in patients with relapsed/refractory lymphoma, but with only modest activity. Recently, we have developed a cyclodextrin-based polymer conjugate of 20-(S)-CPT (IT-101). In this study, we evaluated the preclinical antilymphoma efficacy of IT-101 as compared with CPT-11.

EXPERIMENTAL DESIGN

We determined an in vitro cytotoxicity of IT-101, CPT-11, and their metabolites against multiple human lymphoma cell lines. In human lymphoma xenografts, the pharmacokinetics, inhibitions of tumor DNA topo I catalytic activity, and antilymphoma activities of these compounds were evaluated.

RESULTS

IT-101 and CPT had very high in vitro cytotoxicity against all lymphoma cell lines tested. As compared with CPT-11 and SN-38, IT-101 and CPT had longer release kinetics and significantly inhibit higher tumor DNA topo I catalytic activities. Furthermore, IT-101 showed significantly prolonged the survival of animals bearing s.c. and disseminated human xenografts when compared with CPT-11 at its maximum tolerated dose in mice.

CONCLUSIONS

The promising present results provide the basis for a phase I clinical trial in patients with relapsed/refractory lymphoma.

Polymeric tubulysin-peptide nanoparticles with potent antitumor activity

PURPOSE

Tubulysins are naturally occurring tetrapeptides with potent antiproliferative activity against multiple cancer cell lines. However, they are also highly toxic in animal models. In order to improve the therapeutic index of this class of compounds, a nanoparticle prodrug of tubulysin A (TubA) was synthesized and evaluated in vitro and in vivo.

EXPERIMENTAL DESIGN

A thiol derivative of TubA was covalently attached to a linear, beta-cyclodextrin based polymer through a disulfide linker (CDP-TubA). The polymer conjugate assembled into stable nanoparticles. Inhibition of tubulin polymerization and antiproliferative activity of the polymer conjugate were evaluated in vitro. The preclinical efficacy of CDP-TubA administered i.v. was evaluated in nude mice bearing s.c. implanted human HT29 colorectal and H460 non-small cell lung carcinoma tumors.

RESULTS

The IC(50) of CDP-TubA (in Tub A equivalents) was 24, 5, and 10 nmol/L versus 3, 1, and 2 nmol/L for Tub A in NCI-H1299 (lung), HT-29 (colon), and A2780 (ovarian) cell lines, respectively. Tub A and the active thiol derivative were potent inhibitors of tubulin polymerization, whereas CDP-TubA showed minimal inhibition, indicating that target inhibition requires release of the peptide drug from the nanoparticles. The maximum tolerated dose of CDP-TubA was 6 mg/kg (in TubA equivalents) versus 0.05 mg/kg for TubA in nude mice. In vivo, a single treatment cycle of three weekly doses of CDP-TubA showed a potent antitumor effect and significantly prolonged survival compared with TubA alone.

CONCLUSIONS

Cyclodextrin polymerized nanoparticles are an enabling technology for the safe and effective delivery of tubulysins for the treatment of cancer.

Alpha-methylprednisolone conjugated cyclodextrin polymer-based nanoparticles for rheumatoid arthritis therapy

A glycinate derivative of α-methylprednisolone (MP) was prepared and conjugated to a linear cyclodextrin polymer (CDP) with a loading of 12.4% w/w. The polymer conjugate (CDP-MP) self-assembled into nanoparticles with a size of 27 nm. Release kinetics of MP from the polymer conjugate showed a half-life (t_1/2) of 50 h in phosphate buffer solution (PBS) and 19 h in human plasma. In vitro, the proliferation of human lymphocytes was suppressed to a similar extent but with a delayed effect when CDP-MP was compared with free MP. In vivo, CDP-MP was administered intravenously to mice with collagen-induced arthritis and compared with free MP. CDP-MP was administered weekly for six weeks (0.07, 0.7, and 7 mg/kg/week) and MP was administered daily for six weeks (0.01, 0.1, and 1 mg/kg/day). Body weight changes were minimal in all animals. After 28 days, a significant decrease in arthritis score was observed in animals treated weekly with an intermediate or high dose of CDP-MP. Additionally, dorsoplantar swelling was reduced to baseline in animals treated with CDP-MP at the intermediate and high dose level. Histological evaluation showed a reduction in synovitis, pannus formation and disruption of architecture at the highest dose level of CDP-MP. MP administered daily at equivalent cumulative doses showed minimal efficacy in this model. This study demonstrates that conjugation of MP to a cyclodextrin-polymer may improve its efficacy, leading to lower doses and less frequent administration for a safer and more convenient management of rheumatoid arthritis.

First-in-human phase I trial of a cyclodextrin-containing polymer-camptothecin nanoparticle in patients with solid tumors

14078

Background: IT-101 is a de novo designed experimental therapeutic comprised of linear, cyclodextrin(CD)-containing polymer conjugates of camptothecin(CPT) that assemble into ca. 40 nm diameter nanoparticles via polymer-polymer interactions that involve inclusion complex formation between the CPT and the CD. Particle size, near neutral surface charge and CPT release rate were specifically designed into IT-101. Published pre-clinical animal studies show extended circulation times (t1/2 of ca. 20 h in rodents), tumor accumulation, slow release of the CPT and anti-tumor efficacy that directly correlate to the properties of the nanoparticle. Release of CPT can disassemble the nanoparticle into individual polymer chains that have size ca. 10 nm that are capable of renal clearance (t1/2 of several minutes in rodents). Methods: Patients with relapsed or refractory cancer were evaluated every two cycles of therapy (90 minute IV infusions of IT- 101 in D5W on days 1, 8 and 15 of a 28 day cycle). Three dose levels of 6, 12 and 18 mg CPT eq./m2 have been tested. Results: At the time of this interim analysis, eight patients have been enrolled and five evaluated. In general, IT-101 is well tolerated and pancytopenia is the DLT. The expected MTD is 12 mg/ m2.Three out of five patients demonstrated stable disease on CT scan evaluation. One pancreatic cancer patient remains stable for 6 months. PK data are available from the first 5 patients. Total and free CPT display biphasic elimination from plasma with mean terminal elimination half lives of 38±3.7 and 61±43 hours, respectively. The mean Vd and CLsys of total CPT are 6.1±1.4 L and 0.1±0.03 L/h and are unrelated to dose over the range tested, with a mean total-to-free AUC ratio of 10.7±3.7. Conclusions: These first in human PK data for IT-101 confirm that 40 nm particles with near neutral surface charge provide favorable PK properties. The stable disease rate, although not yet conclusive, is consistent with promising efficacy. The preliminary results of this phase I study warrant continued enrollment that is ongoing.

No significant financial relationships to disclose.

A Solvent-Free Method for Isotopically or Radioactively Labeling Cyclodextrins and Cyclodextrin-Containing Polymers

A method for installing a distinguishable label onto cyclodextrins or cyclodextrin-containing polymers is reported. Cyclodextrins (CD) and cyclodextrin-containing polymers are exposed to labeled (2H or 14C) ethylene oxide (EO) vapor and the alcohol groups on the CD ring open the EO to give ether-linked labeled methylenes and a terminal alcohol. This method provides for the incorporation of an easily tracked and quantified label without the use of solvents or purification steps. The method can be generalized for use with materials that contain nucleophiles other than alcohols, e.g., amines.

Preclinical efficacy of the camptothecin-polymer conjugate IT-101 in multiple cancer models

Preclinical efficacy of i.v. IT-101, a nanoparticulate conjugate of 20(S)-camptothecin and a cyclodextrin-based polymer, was investigated in several mouse xenografts. The effects of different multiple dosing schedules on tumor growth of LS174T colon carcinoma xenografts are elucidated. All multiple dosing schedules administered over 15 to 19 days resulted in enhanced efficacy compared with untreated or single-dose groups. Further improvements in antitumor efficacy were not observed when the dosing frequency was increased from three weekly doses to five doses at 4-day intervals or 5 days of daily dosing followed by 2 days without dosing repeated in three cycles using similar cumulative doses. This observation was attributed to the extended release characteristics of camptothecin from the polymer. Antitumor efficacy was further evaluated in mice bearing six different s.c. xenografts (LS174T and HT29 colorectal cancer, H1299 non-small-cell lung cancer, H69 small-cell lung cancer, Panc-1 pancreatic cancer, and MDA-MB-231 breast cancer) and one disseminated xenograft (TC71-luc Ewing's sarcoma). In all cases, a single treatment cycle of three weekly doses of IT-101 resulted in a significant antitumor effect. Complete tumor regression was observed in all animals bearing H1299 tumors and in the majority of animals with disseminated Ewing's sarcoma tumors. Importantly, IT-101 is effective in a number of tumors that are resistant to treatment with irinotecan (MDA-MB-231, Panc-1, and HT29), consistent with the hypothesis that polymeric drug conjugates may be able to overcome certain kinds of multidrug resistance. Taken together, these results indicate that IT-101 has good tolerability and antitumor activity against a wide range of tumors.

Pharmacokinetics and biodistribution of the camptothecin–polymer conjugate IT-101 in rats and tumor-bearing mice

PURPOSE

IT-101 is a camptothecin-polymer conjugate prepared by linking camptothecin (CPT) to a hydrophilic, cyclodextrin-based, linear polymer through ester bonds. In previous studies, these polymer conjugates with high molecular weights (ca 90 kDa) have shown significant antitumor effects against human colon carcinoma xenografts. The pharmacokinetics of IT-101 in plasma of rats and its biodistribution in nude mice bearing human LS174T colon carcinoma tumors is reported here.

METHODS

Sprague-Dawley rats were injected intravenously with three different doses of IT-101. Serial plasma samples were analyzed for polymer-bound and unconjugated CPT by high-performance liquid chromatography (HPLC). Concentration vs time data were modeled using non-compartmentalized methods and compared to CPT alone injected intravenously at an equivalent dose. Tumor-bearing mice were injected intravenously with IT-101 and intraperitoneally with CPT alone, and sacrificed after 24 and 48 h, and serum, heart, liver, spleen, lungs and tumor collected. Tissue samples were extracted and analyzed for polymer-bound and unconjugated CPT by HPLC.

RESULTS

Plasma concentrations and the area under the curve for polymer-bound CPT are approximately 100-fold higher than those of unconjugated CPT or CPT alone, injected intravenously at an equivalent dose. The plasma half-life of IT-101 ranges from 17 -20 h and is significantly greater than that of CPT alone (1.3 h). When CPT is conjugated to polymer, the biodistribution pattern of CPT is different from that taken alone. At 24 h post injection, the total CPT per gram of tissue is the highest in tumor tissue when compared to all other tissues tested. Tumor concentrations of active CPT released from the conjugate are more than 160-fold higher when administered as a polymer conjugate rather than as CPT alone.

CONCLUSIONS

The studies presented here indicate that intravenous administration of IT-101, a cyclodextrin based polymer-CPT conjugate, gives prolonged plasma half-life and enhanced distribution to tumor tissue when compared to CPT alone. The data also show that active CPT is released from the conjugate within the tumor for an extended period of time. These effects likely play a significant role in the enhanced antitumor activity of IT-101 when compared to CPT alone or irinotecan.

Characterization of Hemodynamic Events Following Intravascular Infusion of Recombinant Adenovirus Reveals Possible Solutions for Mitigating Cardiovascular Responses

Intravascular administration of recombinant adenovirus (rAd) in cancer patients has been well tolerated. However, dose-limiting hemodynamic responses associated with suppression of cardiac output have been observed at doses of 7.5 x 10(13) particles. While analysis of hemodynamic responses induced by small-molecule pharmaceuticals is well established, little is known about the cardiovascular effects of rAd. Telemetric cardiovascular (CV) monitoring in mice was utilized to measure hemodynamic events following intravascular rAd administration. Electrocardiogram analysis revealed a block in the SA node 3-4 min postinfusion, resulting in secondary pacemaking initiated at the AV node. This was associated with acute bradycardia, reduced blood pressure, and hypothermia followed by gradual recovery. Adenovirus-primed murine sera with high neutralizing antibody (nAb) titers could inhibit CV responses, whereas human sera with equivalent nAb titers induced by natural infection were, surprisingly, not inhibitory. Interestingly, repeat dosing within 2-4 h of the primary injection resulted in desensitization, resembling tachyphylaxis, for subsequent CV responses. Last, depletion of Kupffer cells prior to rAd infusion precluded induction of CV responses. These inhibitory effects suggest that rAd interactions with certain cells of the reticular endothelial system are associated with induction of CV responses. Significantly, these studies may provide insight into management of acute adverse effects following rAd systemic delivery, enabling a broadening of therapeutic index.

Characterization of Empty Capsids from a Conditionally Replicating Adenovirus for Gene Therapy

As virus vectors for gene therapy approach the goal of successful clinical treatment, it is increasingly necessary for the product to be fully characterized. Empty capsids are perhaps the main extraneous component of recombinant adenovirus (rAd) products that are purified by column chromatography. Two diverse rAd products, one a replication-defective rAd and the other a conditionally replicating rAd, show different protein compositions of their empty capsids. The empty capsid type from the replication-defective rAd carrying the gene for p53 was previously determined to have approximately 1400 copies per particle of pVIII, the precursor to the hexon-associated protein VIII (Vellekamp et al., Hum. Gene Ther. 2001;12:1923-1936). Quantification of this protein is a useful measure of the amount of empty capsids in preparations of this vector. Here we purify and characterize empty capsids from the conditionally replicating rAd. This empty capsid type lacks any appreciable amount of pVIII but contains pVI and multiple forms of the L1 52/55K protein, mostly as disulfidelinked oligomers. Empty capsid from conditionally replicating rAd present new challenges in terms of its quantification, but sodium dodecyl sulfate-polyacrylamide gel electrophoresis densitometry analysis suggests that the amount of this empty capsid in a preparation, like that of rAd p53 empty capsid, declines with increased time of infection. This empty capsid demonstrates heterogeneity by anion-exchange chromatography, electron microscopy, and CsCl density gradient centrifugation.

Synthetic Biocompatible Cyclodextrin-Based Constructs for Local Gene Delivery to Improve Cutaneous Wound Healing

The localized, sustained delivery of growth factors for wound healing therapy is actively being explored by gene transfer to the wound site. Biocompatible matrices such as bovine collagen have demonstrated usefulness in sustaining gene therapy vectors that express growth factors in local sites for tissue repair. Here, new synthetic biocompatible materials are prepared and shown to deliver a protein to cultured cells via the use of an adenoviral delivery vector. The synthetic construct consists of a linear, beta-cyclodextrin-containing polymer and an adamantane-based cross-linking polymer. When the two polymers are combined, they create an extended network by the formation of inclusion complexes between the cyclodextrins and adamantanes. The properties of the network are altered by controlling the polymer molecular weights and the number of adamantanes on the cross-linking polymer, and these modifications and others such as replacement of the beta-cyclodextrin (host) and adamantane (guest) with other cyclodextrins (hosts such as alpha, gamma, and substituted members) and inclusion complex forming molecules (guests) provide the ability to rationally design network characteristics. Fibroblasts exposed to these synthetic constructs show proliferation rates and migration patterns similar to those obtained with collagen. Gene delivery (green fluorescent protein) to fibroblasts via the inclusion of adenoviral vectors in the synthetic construct is equivalent to levels observed with collagen. These in vitro results suggest that the synthetic constructs are suitable for in vivo tissue repair applications.

Cyclodextrin-Modified Polyethylenimine Polymers for Gene Delivery

Linear and branched poly(ethylenimines), lPEI and bPEI, respectively, grafted with beta-cyclodextrin are prepared to give CD-lPEI and CD-bPEI, respectively, and are investigated as in vitro and in vivo nonviral gene delivery agents. The in vitro toxicity and transfection efficiency are sensitive to the level of cyclodextrin grafting. The cyclodextrin-containing polycations, when combined with adamantane-poly(ethylene glycol) (AD-PEG) conjugates, form particles that are stable at physiological salt concentrations. PEGylated CD-lPEI-based particles give in vitro gene expression equal to or greater than lPEI as measured by the percentage of EGFP expressing cells. Tail vein injections into mice of 120 microg of plasmid DNA formulated with CD-lPEI and AD-PEG do not reveal observable toxicities, and both nucleic acid accumulation and expression are observed in liver.

Development of a formulation that enhances gene expression and efficacy following intraperitoneal administration in rabbits and mice

We conducted a series of experiments to determine if intraperitoneal (IP) delivery of recombinant adenovirus (rAd)-based therapies is improved through carrier vehicle selection, and compared an icodextrin solution (a high molecular weight dextrin with a prolonged peritoneal cavity residence time) with a standardized phosphate buffered saline (PBS) delivery solution. In vitro, comparative adenovirus particle concentration determination (27 h) and bioactivity assay (24h) indicated equivalent compatibility with icodextrin or PBS. In vivo, rabbits treated IP (100 ml) with rAd-betagal 1 x 10(9) P/ml in icodextrin showed improved transgene expression throughout the peritoneal wall compared to rAd-betagal in PBS. In PC-3 tumor-bearing mice treated IP with 5 x 10(9) P/0.5 ml or 1 x 10(10) P/0.5 ml rAd-betagal, transgene expression was significantly enhanced (p < 0.01) with icodextrin compared to PBS in both tumor specimens and peritoneal wall. In subsequent studies we compared prolongation of survival in intraperitoneal PC-3 and MDAH-2774 human xenograft tumor models in nude mice using rAd-p53 in icodextrin or PBS in multi-dose ranging (1 x 10(8) to 1 x 10(10) P) experiments. The icodextrin formulation alone significantly increased rAd-p53 mediated survival (p < 0.05). In animals, these results show that IP rAd gene therapy can be improved with the use of icodextrin, and suggest that prolonged retention and distribution in the peritoneal cavity is an important factor.

Immobilization of oligonucleotides on a large pore support for plasmid purification by triplex affinity interaction

Triplex affinity interaction provides a new process for the purification of plasmid DNA, which is especially suited to meet the demands of a gene therapy use. We developed a method for the functionalization of a large pore affinity support suitable for this application. A 5'-modified DNA oligonucleotide containing an aldehyde group was coupled to adipic acid hydrazide functionalized Sephacryl beads with a yield of 31% (over all immobilization yield 22.6% from starting oligonucleotide). The resulting selective and covalent immobilization of the ligand via a 16 atom, hydrophilic linker arm enables the oligonucleotide bases to freely bind to the target sequence. The proposed method provides affinity supports that might be used in large scale affinity purification of plasmid DNA.

Purification of plasmids by triplex affinity interaction

Production of pharmaceutical grade plasmid DNA is an important issue in gene therapy. We developed a method for affinity purification of plasmids by triple helix interaction. This method is based on sequence-specific binding of an oligonucleotide immobilized on a large pore chromatography support to a target sequence on the plasmid. Using design criteria derived from thermodynamic data, we produced a 15mer target sequence which binds strongly to the affinity support under mildly acidic conditions. Plasmid DNA was purified from clarified Escherichia coli lysate by incubation with the affinity beads at pH 5.0 and high NaCl concentration. After extensive washing of the beads, purified plasmid DNA was eluted with alkaline buffer. The purified plasmid showed no RNA or cell DNA contamination in HPLC analysis and total protein concentration was reduced considerably. Due to its mechanical stability and porosity this support can be used in a continuous affinity purification process, which has a high potential for scale up.

Preparative purification of supercoiled plasmid DNA using anion-exchange chromatography

Large scale manufacturing of gene vectors such as plasmid DNA is an important issue in gene therapy. Anion-exchange chromatography is fundamental in the downstream processing of plasmids both as a process and analytical technique. This work reports the use of Q-Sepharose columns (1, 10 and 40 ml) for the preparative purification of plasmid pUC18. NaCl gradient elution enabled the isolation of supercoiled plasmid from low-M(r) RNA, cDNA and plasmid variants. A compact covalently closed, supercoiled form of denatured plasmid carrying large stretches of single-stranded DNA was identified as one of the major contaminants. Anion-exchange HPLC on a Poros QE 20 column was used to quantify plasmid yield. Supercoiled plasmid was recovered in a single fraction with a 62 +/- 8% yield. Loadings higher than 40 micrograms/ml gel could be used but at the expense of a loss of resolution between open circular and supercoiled forms. Plasmid quality was evaluated by gel electrophoresis, restriction analysis, transformation experiments and protein assays.