A single dose of self-transcribing and replicating RNA-based SARS-CoV-2 vaccine produces protective adaptive immunity in mice.

A self-transcribing and replicating RNA (STARR)-based vaccine (LUNAR-COV19) has been developed to prevent SARS-CoV-2 infection. The vaccine encodes an alphavirus-based replicon and the SARS-CoV-2 full-length spike glycoprotein. Translation of the replicon produces a replicase complex that amplifies and prolongs SARS-CoV-2 spike glycoprotein expression. A single prime vaccination in mice led to robust antibody responses, with neutralizing antibody titers increasing up to day 60. Activation of cell-mediated immunity produced a strong viral antigen-specific CD8+ T lymphocyte response. Assaying for intracellular cytokine staining for interferon (IFN)γ and interleukin-4 (IL-4)-positive CD4+ T helper (Th) lymphocytes as well as anti-spike glycoprotein immunoglobulin G (IgG)2a/IgG1 ratios supported a strong Th1-dominant immune response. Finally, single LUNAR-COV19 vaccination at both 2 µg and 10 µg doses completely protected human ACE2 transgenic mice from both mortality and even measurable infection following wild-type SARS-CoV-2 challenge. Our findings collectively suggest the potential of LUNAR-COV19 as a single-dose vaccine.

Genotoxicity and carcinogenicity risk assessment of prucalopride, a selective 5-hydroxytryptamine 4 receptor agonist.

Prucalopride, a high affinity, selective serotonin type 4 (5-HT4) receptor agonist, was associated with increased neoplasia incidence (in endocrine tissues and liver) in 2-year rodent bioassays, without evidence of a genotoxic mechanism of action. Proposed mechanisms of action involve prolactin and the constitutive androstane receptor (CAR). Epigenetic mechanisms and their relevance to humans are discussed. Data from in vitro and in vivo rodent studies demonstrated that prucalopride-related stimulation of prolactin secretion (via dopamine receptor D2 antagonism at high doses) is a rodent-specific, non-genotoxic mechanism for inducing hyperplasia and neoplasia in prolactin receptor-expressing endocrine tissues. Additional data demonstrated that CAR-mediated liver enzyme induction underlies the observed hepatocellular adenomas and thyroid follicular adenomas in rodents. A 12-month neonatal mouse carcinogenicity study confirmed the lack of a genotoxic mechanism of action. Furthermore, tumors were observed only at very high exposures (200 and 63 fold higher in mice and rats, respectively, than human exposure after a daily therapeutic dose of 2 mg). The studies indicate that non-genotoxic, rodent-specific, epigenetic mechanisms that are considered clinically irrelevant are responsible for the increased incidence of neoplasias associated with very high exposure to prucalopride in rodents, and that prucalopride does not pose a carcinogenic safety risk to humans.

Current strategies in the non-clinical safety assessment of biologics: New targets, new molecules, new challenges.

Nonclinical safety testing of biopharmaceuticals can present significant challenges to human risk assessment with these innovative and often complex drugs. Emerging topics in this field were discussed recently at the 2016 Annual US BioSafe General Membership meeting. The presentations and subsequent discussions from the main sessions are summarized. The topics covered included: (i) specialty biologics (oncolytic virus, gene therapy, and gene editing-based technologies), (ii) the value of non-human primates (NHPs) for safety assessment, (iii) challenges in the safety assessment of immuno-oncology drugs (T cell-dependent bispecifics, checkpoint inhibitors, and costimulatory agonists), (iv) emerging therapeutic approaches and modalities focused on microbiome, oligonucleotide, messenger ribonucleic acid (mRNA) therapeutics, (v) first in human (FIH) dose selection and the minimum anticipated biological effect level (MABEL), (vi) an update on current regulatory guidelines, International Council for Harmonization (ICH) S1, S3a, S5, S9 and S11 and (vii) breakout sessions that focused on bioanalytical and PK/PD challenges with bispecific antibodies, cytokine release in nonclinical studies, determining adversity and NOAEL for biologics, the value of second species for toxicology assessment and what to do if there is no relevant toxicology species.

Workshop Proceedings: Streamlined Development of Safety Assessment Programs Supporting Orphan/Rare Diseases-Are We There Yet?

A workshop entitled "Streamlined Development of Safety Assessment Programs Supporting Orphan/Rare Diseases-Are We There Yet?" was held at the 36th Annual Meeting of the American College of Toxicology in Summerlin, Nevada. The workshop was sponsored by Shire and Ultragenyx and was designed to present the nonclinical considerations for the development of various products for rare diseases. A panel of experts from industry and government highlighted the nonclinical considerations in developing toxicology programs supporting rare disease therapeutics, challenges in preclinical safety assessment, reviewed the current guidance, and presented the progress that has been made to date. The main learning from the workshop was that nonclinical testing of therapeutics targeting rare disease warrants special considerations, and early collaboration between sponsors and health authorities may help optimize the scope and timing of the supportive studies. Specific examples for nonclinical development programs for enzyme replacement therapy (ERT) were presented. Although the symposium focused on ERTs, the concepts are broadly applicable.

Microscopic background changes in brains of cynomolgus monkeys.

Brain sections from control cynomolgus monkeys (Macaca fascicularis) used in toxicology studies were evaluated retrospectively in order to better understand spontaneous background changes in this species. Hematoxylin and eosin-stained slides from 76 animals (38 males and 38 females) of 9 studies were examined. Eleven animals (9 males and 2 females) were each observed to have 1 to 3 findings within the brain sections examined, for a total of 19 findings. No findings were noted in the spinal cord. The most common finding was focal to multifocal perivascular infiltration of mononuclear cells, affecting the parenchyma, the meninges, or the choroid plexus. Additionally, focal gliosis was observed in 6 animals and a single focus of hemosiderin deposition (coincident with focal gliosis and mononuclear cell infiltrate) was noted in 1 animal. Most of the glial foci were composed of cells consistent with microglial cells, with or without admixed lymphocytes. All findings were of slight or minimal severity, lacked an apparent cause, and were considered incidental and of negligible biologic significance. An awareness of the spontaneous incidence of these background findings may facilitate the discernment of toxicologically relevant effects when these findings are observed.

Safety, immunogenicity and efficacy of the self-amplifying mRNA ARCT-154 COVID-19 vaccine: pooled phase 1, 2, 3a and 3b randomized, controlled trials.

Combination of waning immunity and lower effectiveness against new SARS-CoV-2 variants of approved COVID-19 vaccines necessitates new vaccines. We evaluated two doses, 28 days apart, of ARCT-154, a self-amplifying mRNA COVID-19 vaccine, compared with saline placebo in an integrated phase 1/2/3a/3b controlled, observer-blind trial in Vietnamese adults (ClinicalTrial.gov identifier: NCT05012943). Primary safety and reactogenicity outcomes were unsolicited adverse events (AE) 28 days after each dose, solicited local and systemic AE 7 days after each dose, and serious AEs throughout the study. Primary immunogenicity outcome was the immune response as neutralizing antibodies 28 days after the second dose. Efficacy against COVID-19 was assessed as primary and secondary outcomes in phase 3b. ARCT-154 was well tolerated with generally mild-moderate transient AEs. Four weeks after the second dose 94.1% (95% CI: 92.1-95.8) of vaccinees seroconverted for neutralizing antibodies, with a geometric mean-fold rise from baseline of 14.5 (95% CI: 13.6-15.5). Of 640 cases of confirmed COVID-19 eligible for efficacy analysis most were due to the Delta (B.1.617.2) variant. Efficacy of ARCT-154 was 56.6% (95% CI: 48.7- 63.3) against any COVID-19, and 95.3% (80.5-98.9) against severe COVID-19. ARCT-154 vaccination is well tolerated, immunogenic and efficacious, particularly against severe COVID-19 disease.

In vivo pharmacology and toxicology evaluation of polyethylene glycol-conjugated interferon beta-1a.

Human interferon (IFN) ß has well established beneficial effects in treating relapsing forms of multiple sclerosis, but current first-line treatment requires frequent (from daily to weekly) parenteral administration. A 20-kDa polyethylene glycol (PEG)-conjugated IFN ß-1a (PEG-IFN ß-1a) is being developed to decrease the frequency of administration and improve patient convenience and compliance. We present pharmacokinetic (PK) and pharmacodynamic (PD) parameters, immunogenicity, and safety of PEG-IFN ß-1a in Rhesus monkeys in support of a phase 1 clinical trial. Two single-dose PK/PD studies and one 5-week repeat-dose toxicity study compliant with good laboratory practice were conducted. The PK of IFN ß-1a and PEG-IFN ß-1a were modeled with a two-compartment model, and the link between drug concentration and neopterin response (PD marker) was described with an indirect stimulatory model. PEG-IFN ß-1a showed greater exposure, longer half-life, lower clearance, and reduced volume of distribution than unmodified IFN ß-1a. Consistent with the pharmacology of type I IFNs, PEG-IFN ß-1a resulted in the elevation of neopterin concentration, a transient body temperature increase, and a reversible lymphocyte count decrease. As expected, neutralizing antibodies to PEG-IFN ß-1a formed in almost all monkeys after 5 weeks of treatment, which resulted in significantly reduced drug exposure and abrogation of neopterin induction. There were no drug-related adverse effects at doses up to 100 µg/kg (11 MIU/kg) given subcutaneously or intramuscularly once weekly for 5 weeks. The no-observed-adverse-effect level was determined to be 100 µg/kg (11 MIU/kg), the highest dose tested.

Carcinogenicity assessments of biotechnology-derived pharmaceuticals: a review of approved molecules and best practice recommendations.

An important safety consideration for developing new therapeutics is assessing the potential that the therapy will increase the risk of cancer. For biotherapeutics, traditional two-year rodent bioassays are often not scientifically applicable or feasible. This paper is a collaborative effort of industry toxicologists to review past and current practice regarding carcinogenicity assessments of biotherapeutics and to provide recommendations. Publicly available information on eighty marketed protein biotherapeutics was reviewed. In this review, no assessments related to carcinogenicity or tumor growth promotion were identified for fifty-one of the eighty molecules. For the twenty-nine biotherapeutics in which assessments related to carcinogenicity were identified, various experimental approaches were employed. This review also discusses several key principles to aid in the assessment of carcinogenic potential, including (1) careful consideration of mechanism of action to identify theoretical risks, (2) careful investigation of existing data for indications of proliferative or immunosuppressive potential, and (3) characterization of any proliferative or immunosuppressive signals detected. Traditional two-year carcinogenicity assays should not be considered as the default method for assessing the carcinogenicity potential of biotherapeutics. If experimentation is considered warranted, it should be hypothesis driven and may include a variety of experimental models. Ultimately, it is important that preclinical data provide useful guidance in product labeling.

Safety, tolerability, and lack of antibody responses after administration of a PfCSP DNA malaria vaccine via needle or needle-free jet injection, and comparison of intramuscular and combination intramuscular/intradermal routes.

Introduction of a new vaccine requires choosing a delivery system that provides safe administration and the desired level of immunogenicity. The safety, tolerability, and immunogenicity of three monthly 2.5-mg doses of a PfCSP DNA vaccine were evaluated in healthy volunteers as administered intramuscularly (IM) by needle, IM by jet injection (Biojector or IM/intradermally (ID) by jet injection. Vaccine administration was well-tolerated. Adverse events were primarily mild and limited to the site of injection (98%). Jet injections (either IM or ID) were associated with approximately twice as many adverse events per immunization as needle IM, but nevertheless were strongly and consistently preferred in opinion polls taken during the study. No volunteers had clinically significant biochemical or hematologic changes or detectable anti-dsDNA antibodies. In conclusion, the injection of Plasmodium falciparum circumsporozoite (PfCSP) DNA vaccine appeared to be safe and well-tolerated when administered by any of the three modes of delivery. However, despite improved antibody responses following both jet injection and ID delivery in animal models, no antibodies could be detected in volunteers by immunofluorescence antibody test (IFAT) or enzyme-linked immunosorbent assay (ELISA) after DNA vaccination.

Immunotoxicity profile of natalizumab.

Natalizumab is a monoclonal antibody to human alpha4 integrin indicated for treatment of multiple sclerosis and Crohn's disease that prevents extravasation of leukocytes into surrounding tissues and their involvement in inflammation. Because alpha4 integrins and their receptors are involved in hematopoiesis and immune cell trafficking, natalizumab may interfere with these processes. We evaluated the effects of natalizumab on immune function in monkeys using in vitro and in vivo studies. Consistent with the pharmacologic effects of natalizumab, dose-related increases in white blood cell counts and spleen weights were observed. Administration to monkeys did not result in statistically significant alterations in the percentages of circulating B-cells, T-cells, T-cell subsets (CD4, CD8), or stem cells (CD34). A modest and highly variable delay in the primary humoral response to T-cell-dependent antigens was observed. Ex vivo studies using cells from natalizumab-treated monkeys demonstrated that treatment did not alter immune regulatory or effector cell functions in blood lymphocytes or spleen cells. A similar lack of effect on these functions was observed in vitro following treatment of PBMC and monocytes from human donors. Overall, natalizumab was well tolerated in monkeys, demonstrated the expected pharmacologic effect on cell trafficking, and showed no adverse effect on immune cell function.

The development of a bicistronic plasmid DNA vaccine for B-cell lymphoma.

Tumor vaccines are a promising alternative to chemotherapy for the treatment of metastatic cancer. To be effective and safe, a therapeutic cancer vaccine should specifically target antigens expressed only on metastatic tumor cells. A vaccine directed against the unique surface immunoglobulin or idiotype expressed on non-Hodgkin's B-cell lymphoma fulfills these criteria, as both primary and metastatic tumor cells express tumor specific immunoglobulins. Using the murine 38C13 B-cell lymphoma tumor as a model system, a plasmid DNA vaccine was designed to express a bicistronic mRNA encoding both the light and heavy tumor immunoglobulin (idiotype) proteins expressed on the surface of the 38C13 tumor. To increase the immunogenicity of the plasmid DNA vaccine, each of the murine variable domains (light and heavy) were fused to their respective human immunoglobulin constant domains. In addition, a eukaryotic expression cassette was constructed to effect both high-level expression of the mouse/human chimeric immunoglobulin, and to elicit a protective immune response in vivo. Unique Sfi I restriction sites were used for the rapid cloning of any tumor specific immunoglobulin idiotype domains and a series of plasmid constructs were made to test changes to the J domain and/or the human C domain to insert the Sfi I restriction sites. Such changes were found to have significant effects on both expression and immunogenicity. Vaccination of mice with prototype idiotype vaccines was found to generate a protective immune response to the 38C13 tumor. This study indicates that a novel bicistronic plasmid DNA-based vaccine can be used to develop a tumor specific vaccine against B-cell lymphoma.