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.

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.

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.).

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.

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."

Correlating preclinical animal studies and human clinical trials of a multifunctional, polymeric nanoparticle.

Nanoparticles are currently being investigated in a number of human clinical trials. As information on how nanoparticles function in humans is difficult to obtain, animal studies that can be correlative to human behavior are needed to provide guidance for human clinical trials. Here, we report correlative studies on animals and humans for CRLX101, a 20- to 30-nm-diameter, multifunctional, polymeric nanoparticle containing camptothecin (CPT). CRLX101 is currently in phase 2 clinical trials, and human data from several of the clinical investigations are compared with results from multispecies animal studies. The pharmacokinetics of polymer-conjugated CPT (indicative of the CRLX101 nanoparticles) in mice, rats, dogs, and humans reveal that the area under the curve scales linearly with milligrams of CPT per square meter for all species. Plasma concentrations of unconjugated CPT released from CRLX101 in animals and humans are consistent with each other after accounting for differences in serum albumin binding of CPT. Urinary excretion of polymer-conjugated CPT occurs primarily within the initial 24 h after dosing in animals and humans. The urinary excretion dynamics of polymer-conjugated and unconjugated CPT appear similar between animals and humans. CRLX101 accumulates into solid tumors and releases CPT over a period of several days to give inhibition of its target in animal xenograft models of cancer and in the tumors of humans. Taken in total, the evidence provided from animal models on the CRLX101 mechanism of action suggests that the behavior of CRLX101 in animals is translatable to humans.

First-in-human phase 1/2a trial of CRLX101, a cyclodextrin-containing polymer-camptothecin nanopharmaceutical in patients with advanced solid tumor malignancies.

Patients with advanced solid malignancies were enrolled to an open-label, single-arm, dose-escalation study, in which CRLX101 was administered intravenously over 60 min among two dosing schedules, initially weekly at 6, 12, and 18 mg/m(2) and later bi-weekly at 12, 15, and 18 mg/m(2). The maximum tolerated dose (MTD) was determined at 15 mg/m(2) bi-weekly, and an expansion phase 2a study was completed. Patient samples were obtained for pharmacokinetic (PK) and pharmacodynamic (PD) assessments. Response was evaluated per RECIST criteria v1.0 every 8 weeks. Sixty-two patients (31 male; median age 63 years, range 39-79) received treatment. Bi-weekly dosing was generally well tolerated with myelosuppression being the dose-limiting toxicity. Among all phase 1/2a patients receiving the MTD (n = 44), most common grade 3/4 adverse events were neutropenia and fatigue. Evidence of systemic plasma exposure to both the polymer-conjugated and unconjugated CPT was observed in all treated patients. Mean elimination unconjugated CPT Tmax values ranged from 17.7 to 24.5 h, and maximum plasma concentrations and areas under the curve were generally proportional to dose for both polymer-conjugated and unconjugated CPT. Best overall response was stable disease in 28 patients (64 %) treated at the MTD and 16 (73 %) of a subset of NSCLC patients. Median progression-free survival (PFS) for patients treated at the MTD was 3.7 months and for the subset of NSCLC patients was 4.4 months. These combined phase 1/2a data demonstrate encouraging safety, pharmacokinetic, and efficacy results. Multinational phase 2 clinical development of CRLX101 across multiple tumor types is ongoing.

Cyclodextrin-containing polymers: versatile platforms of drug delivery materials.

Nanoparticles are being widely explored as potential therapeutics for numerous applications in medicine and have been shown to significantly improve the circulation, biodistribution, efficacy, and safety profiles of multiple classes of drugs. One leading class of nanoparticles involves the use of linear, cyclodextrin-containing polymers (CDPs). As is discussed in this paper, CDPs can incorporate therapeutic payloads into nanoparticles via covalent attachment of prodrug/drug molecules to the polymer (the basis of the Cyclosert platform) or by noncovalent inclusion of cationic CDPs to anionic, nucleic acid payloads (the basis of the RONDEL platform). For each of these two approaches, we review the relevant molecular architecture and its rationale, discuss the physicochemical and biological properties of these nanoparticles, and detail the progress of leading drug candidates for each that have achieved clinical evaluation. Finally, we look ahead to potential future directions of investigation and product candidates based upon this technology.

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.

Tumor-associated macrophages are predominant carriers of cyclodextrin-based nanoparticles into gliomas.

The goal of this study was to evaluate the mechanism of cyclodextrin-based nanoparticle (CDP-NP) uptake into a murine glioma model. Using mixed in vitro culture systems, we demonstrated that CDP-NPs were preferentially taken up by BV2 and N9 microglia (MG) cells compared with GL261 glioma cells. Fluorescent microscopy and flow cytometry analysis of intracranial GL261 gliomas confirmed these findings and demonstrated a predominant CDP-NP uptake by macrophages (MPs) and MG within and around the tumor site. Notably, in mice bearing bilateral intracranial tumor, MG and MPs carrying CDP-NPs were able to migrate to the contralateral tumors. In conclusion, these studies better characterize the cellular distribution of CDP-NPs in intracranial tumors and demonstrate that MPs and MG could potentially be used as nanoparticle drug carriers into malignant brain tumors. FROM THE CLINICAL EDITOR: The goal of this study was to evaluate the mechanism of cyclodextrin-based nanoparticle (CDP-NP) uptake into a murine glioma model. CDP-NP was preferentially taken up microglia (MG) cells as compared to glioma cells. A predominant CDP-NP uptake by macrophages and MG was also shown in and around the tumor site. Macrophages and MG could potentially be used as nanoparticle drug carriers into malignant brain tumors.

Pharmacokinetics and tumor dynamics of the nanoparticle IT-101 from PET imaging and tumor histological measurements.

IT-101, a cyclodextrin polymer-based nanoparticle containing camptothecin, is in clinical development for the treatment of cancer. Multiorgan pharmacokinetics and accumulation in tumor tissue of IT-101 is investigated by using PET. IT-101 is modified through the attachment of a 1,4,7,10-tetraazacyclododecane-1,4,7-Tris-acetic acid ligand to bind (64)Cu(2+). This modification does not affect the particle size and minimally affects the surface charge of the resulting nanoparticles. PET data from (64)Cu-labeled IT-101 are used to quantify the in vivo biodistribution in mice bearing Neuro2A s.c. tumors. The (64)Cu-labeled IT-101 displays a biphasic plasma elimination. Approximately 8% of the injected dose is rapidly cleared as a low-molecular-weight fraction through the kidneys. The remaining material circulates in plasma with a terminal half-life of 13.3 h. Steadily increasing concentrations, up to 11% injected dose per cm(3), are observed in the tumor over 24 h, higher than any other tissue at that time. A 3-compartment model is used to determine vascular permeability and nanoparticle retention in tumors, and is able to accurately represent the experimental data. The calculated tumor vascular permeability indicates that the majority of nanoparticles stay intact in circulation and do not disassemble into individual polymer strands. A key assumption to modeling the tumor dynamics is that there is a "sink" for the nanoparticles within the tumor. Histological measurements using confocal microscopy show that IT-101 localizes within tumor cells and provides the sink in the tumor for the nanoparticles.

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 alpha-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 (t1/2) 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.