Jeremy D. Heidel

Bio: Jeremy D. Heidel is an academic researcher from California Institute of Technology. The author has contributed to research in topics: Small interfering RNA & Gene delivery. The author has an hindex of 16, co-authored 25 publications receiving 5372 citations.

Evidence of RNAi in humans from systemically administered siRNA via targeted nanoparticles

Abstract: Therapeutics that are designed to engage RNA interference (RNAi) pathways have the potential to provide new, major ways of imparting therapy to patients. Long, double-stranded RNAs were first shown to mediate RNAi in Caenorhabditis elegans, and the potential use of RNAi for human therapy has been demonstrated by the finding that small interfering RNAs (siRNAs; approximately 21-base-pair double-stranded RNA) can elicit RNAi in mammalian cells without producing an interferon response. We are at present conducting the first in-human phase I clinical trial involving the systemic administration of siRNA to patients with solid cancers using a targeted, nanoparticle delivery system. Here we provide evidence of inducing an RNAi mechanism of action in a human from the delivered siRNA. Tumour biopsies from melanoma patients obtained after treatment show the presence of intracellularly localized nanoparticles in amounts that correlate with dose levels of the nanoparticles administered (this is, to our knowledge, a first for systemically delivered nanoparticles of any kind). Furthermore, a reduction was found in both the specific messenger RNA (M2 subunit of ribonucleotide reductase (RRM2)) and the protein (RRM2) levels when compared to pre-dosing tissue. Most notably, we detect the presence of an mRNA fragment that demonstrates that siRNA-mediated mRNA cleavage occurs specifically at the site predicted for an RNAi mechanism from a patient who received the highest dose of the nanoparticles. Together, these data demonstrate that siRNA administered systemically to a human can produce a specific gene inhibition (reduction in mRNA and protein) by an RNAi mechanism of action.

Sequence-Specific Knockdown of EWS-FLI1 by Targeted, Nonviral Delivery of Small Interfering RNA Inhibits Tumor Growth in a Murine Model of Metastatic Ewing's Sarcoma

Abstract: The development of effective, systemic therapies for metastatic cancer is highly desired. We show here that the systemic delivery of sequence-specific small interfering RNA (siRNA) against the EWS-FLI1 gene product by a targeted, nonviral delivery system dramatically inhibits tumor growth in a murine model of metastatic Ewing's sarcoma. The nonviral delivery system uses a cyclodextrin-containing polycation to bind and protect siRNA and transferrin as a targeting ligand for delivery to transferrin receptor-expressing tumor cells. Removal of the targeting ligand or the use of a control siRNA sequence eliminates the antitumor effects. Additionally, no abnormalities in interleukin-12 and IFN-alpha, liver and kidney function tests, complete blood counts, or pathology of major organs are observed from long-term, low-pressure, low-volume tail-vein administrations. These data provide strong evidence for the safety and efficacy of this targeted, nonviral siRNA delivery system.

Functional polarity is introduced by Dicer processing of short substrate RNAs

Abstract: Synthetic RNA duplexes that are substrates for Dicer are potent triggers of RNA interference (RNAi). Blunt 27mer duplexes can be up to 100-fold more potent than traditional 21mer duplexes (1). Not all 27mer duplexes show increased potency. Evaluation of the products of in vitro dicing reactions using electrospray ionization mass spectrometry reveals that a variety of products can be produced by Dicer cleavage. Use of asymmetric duplexes having a single 2-base 3′-overhang restricts the heterogeneity that results from dicing. Inclusion of DNA residues at the ends of blunt duplexes also limits heterogeneity. Combination of asymmetric 2-base 3′-overhang with 3′-DNA residues on the blunt end result in a duplex form which directs dicing to predictably yield a single primary cleavage product. It is therefore possible to design a 27mer duplex which is processed by Dicer to yield a specific, desired 21mer species. Using this strategy, two different 27mers can be designed that result in the same 21mer after dicing, one where the 3′-overhang resides on the antisense (AS) strand and dicing proceeds to the ‘right’ (‘R’) and one where the 3′-overhang resides on the sense (S) strand and dicing proceeds to the ‘left’ (‘L’). Interestingly, the ‘R’ version of the asymmetric 27mer is generally more potent in reducing target gene levels than the ‘L’ version 27mer. Strand targeting experiments show asymmetric strand utilization between the two different 27mer forms, with the ‘R’ form favoring S strand and the ‘L’ form favoring AS strand silencing. Thus, Dicer processing confers functional polarity within the RNAi pathway.

Administration in non-human primates of escalating intravenous doses of targeted nanoparticles containing ribonucleotide reductase subunit M2 siRNA

Abstract: The results of administering escalating, i.v. doses of targeted nanoparticles containing a siRNA targeting the M2 subunit of ribonucleotide reductase to non-human primates are reported. The nanoparticles consist of a synthetic delivery system that uses a linear, cyclodextrin-containing polycation, transferrin (Tf) protein targeting ligand, and siRNA. When administered to cynomolgus monkeys at doses of 3 and 9 mg siRNA/kg, the nanoparticles are well tolerated. At 27 mg siRNA/kg, elevated levels of blood urea nitrogen and creatinine are observed that are indicative of kidney toxicity. Mild elevations in alanine amino transferase and aspartate transaminase at this dose level indicate that the liver is also affected to some extent. Analysis of complement factors does not reveal any changes that are clearly attributable to dosing with the nanoparticle formulation. Detection of increased IL-6 levels in all animals at 27 mg siRNA/kg and increased IFN-γ in one animal indicate that this high dose level produces a mild immune response. Overall, no clinical signs of toxicity clearly attributable to treatment are observed. The multiple administrations spanning a period of 17–18 days enable assessment of antibody formation against the human Tf component of the formulation. Low titers of anti-Tf antibodies are detected, but this response is not associated with any manifestations of a hypersensitivity reaction upon readministration of the targeted nanoparticle. Taken together, the data presented show that multiple, systemic doses of targeted nanoparticles containing nonchemically modified siRNA can safely be administered to non-human primates.

Correlating animal and human phase Ia/Ib clinical data with CALAA-01, a targeted, polymer-based nanoparticle containing siRNA

Abstract: Nanoparticle-based experimental therapeutics are currently being investigated in numerous human clinical trials. CALAA-01 is a targeted, polymer-based nanoparticle containing small interfering RNA (siRNA) and, to our knowledge, was the first RNA interference (RNAi)–based, experimental therapeutic to be administered to cancer patients. Here, we report the results from the initial phase I clinical trial where 24 patients with different cancers were treated with CALAA-01 and compare those results to data obtained from multispecies animal studies to provide a detailed example of translating this class of nanoparticles from animals to humans. The pharmacokinetics of CALAA-01 in mice, rats, monkeys, and humans show fast elimination and reveal that the maximum concentration obtained in the blood after i.v. administration correlates with body weight across all species. The safety profile of CALAA-01 in animals is similarly obtained in humans except that animal kidney toxicities are not observed in humans; this could be due to the use of a predosing hydration protocol used in the clinic. Taken in total, the animal models do appear to predict the behavior of CALAA-01 in humans.

Nanoparticle therapeutics: an emerging treatment modality for cancer

Abstract: Nanoparticles — particles in the size range 1–100 nm — are emerging as a class of therapeutics for cancer. Early clinical results suggest that nanoparticle therapeutics can show enhanced efficacy, while simultaneously reducing side effects, owing to properties such as more targeted localization in tumours and active cellular uptake. Here, we highlight the features of nanoparticle therapeutics that distinguish them from previous anticancer therapies, and describe how these features provide the potential for therapeutic effects that are not achievable with other modalities. While large numbers of preclinical studies have been published, the emphasis here is placed on preclinical and clinical studies that are likely to affect clinical investigations and their implications for advancing the treatment of patients with cancer.

Cancer nanomedicine: progress, challenges and opportunities.

Abstract: The intrinsic limits of conventional cancer therapies prompted the development and application of various nanotechnologies for more effective and safer cancer treatment, herein referred to as cancer nanomedicine. Considerable technological success has been achieved in this field, but the main obstacles to nanomedicine becoming a new paradigm in cancer therapy stem from the complexities and heterogeneity of tumour biology, an incomplete understanding of nano-bio interactions and the challenges regarding chemistry, manufacturing and controls required for clinical translation and commercialization. This Review highlights the progress, challenges and opportunities in cancer nanomedicine and discusses novel engineering approaches that capitalize on our growing understanding of tumour biology and nano-bio interactions to develop more effective nanotherapeutics for cancer patients.

Analysis of nanoparticle delivery to tumours

Abstract: This Perspective explores and explains the fundamental dogma of nanoparticle delivery to tumours and answers two central questions: ‘how many nanoparticles accumulate in a tumour?’ and ‘how does this number affect the clinical translation of nanomedicines?’

Strategies in the design of nanoparticles for therapeutic applications

Abstract: Engineered nanoparticles have the potential to revolutionize the diagnosis and treatment of many diseases; for example, by allowing the targeted delivery of a drug to particular subsets of cells. However, so far, such nanoparticles have not proved capable of surmounting all of the biological barriers required to achieve this goal. Nevertheless, advances in nanoparticle engineering, as well as advances in understanding the importance of nanoparticle characteristics such as size, shape and surface properties for biological interactions, are creating new opportunities for the development of nanoparticles for therapeutic applications. This Review focuses on recent progress important for the rational design of such nanoparticles and discusses the challenges to realizing the potential of nanoparticles.

MicroRNA therapeutics: towards a new era for the management of cancer and other diseases

Abstract: MicroRNAs (miRNAs) are small non-coding RNAs that can modulate mRNA expression. Insights into the roles of miRNAs in development and disease have led to the development of new therapeutic approaches that are based on miRNA mimics or agents that inhibit their functions (antimiRs), and the first such approaches have entered the clinic. This Review discusses the role of different miRNAs in cancer and other diseases, and provides an overview of current miRNA therapeutics in the clinic. In just over two decades since the discovery of the first microRNA (miRNA), the field of miRNA biology has expanded considerably. Insights into the roles of miRNAs in development and disease, particularly in cancer, have made miRNAs attractive tools and targets for novel therapeutic approaches. Functional studies have confirmed that miRNA dysregulation is causal in many cases of cancer, with miRNAs acting as tumour suppressors or oncogenes (oncomiRs), and miRNA mimics and molecules targeted at miRNAs (antimiRs) have shown promise in preclinical development. Several miRNA-targeted therapeutics have reached clinical development, including a mimic of the tumour suppressor miRNA miR-34, which reached phase I clinical trials for treating cancer, and antimiRs targeted at miR-122, which reached phase II trials for treating hepatitis. In this article, we describe recent advances in our understanding of miRNAs in cancer and in other diseases and provide an overview of current miRNA therapeutics in the clinic. We also discuss the challenge of identifying the most efficacious therapeutic candidates and provide a perspective on achieving safe and targeted delivery of miRNA therapeutics.