Immunogenicity and Efficacy of TNX-1800, A Live Virus Recombinant Poxvirus Vaccine Candidate, against SARS-CoV-2 Challenge in Nonhuman Primates.

TNX-1800 is a synthetically derived live recombinant chimeric horsepox virus (rcHPXV) vaccine candidate expressing Wuhan SARS-CoV-2 spike (S) protein. The primary objective of this study was to evaluate the immunogenicity and efficacy of TNX-1800 in two nonhuman primate species challenged with USA-WA1/2020 SARS-CoV-2. TNX-1800 vaccination was well tolerated with no serious adverse events or significant changes in clinical parameters. A single dose of TNX-1800 generated humoral responses in African Green Monkeys and Cynomolgus Macaques, as measured by the total binding of anti-SARS-CoV-2 S IgG and neutralizing antibody titers against the USA-WA1/2020 strain. In addition, a single dose of TNX-1800 induced an interferon-gamma (IFN-γ)-mediated T-cell response in Cynomolgus Macaques. Following challenge with SARS-CoV-2, African Green and Cynomolgus Macaques exhibited rapid clearance of virus in the upper and lower respiratory tract. Future studies will assess the efficacy of TNX-1800 against newly emerging variants and demonstrate its safety in humans.

TNX-1500, a crystallizable fragment-modified anti-CD154 antibody, prolongs nonhuman primate renal allograft survival.

The blockade of the CD154-CD40 pathway with anti-CD154 monoclonal antibody has been a promising immunomodulatory approach to prevent allograft rejection. However, clinical trials of immunoglobulin G1 antibodies targeting this pathway revealed thrombogenic properties, which were subsequently shown to be mediated by crystallizable fragment (Fc)-gamma receptor IIa-dependent platelet activation. To prevent thromboembolic complications, an immunoglobulin G4 anti-CD154 monoclonal antibody, TNX-1500, which retains the fragment antigen binding region of ruplizumab (humanized 5c8, BG9588), was modified by protein engineering to decrease Fc binding to Fc-gamma receptor IIa while retaining certain other effector functions and pharmacokinetics comparable with natural antibodies. Here, we report that TNX-1500 treatment is not associated with platelet activation in vitro and consistently inhibits kidney allograft rejection in vivo without clinical or histologic evidence of prothrombotic phenomena. We conclude that TNX-1500 retains efficacy similar to that of 5c8 to prevent kidney allograft rejection while avoiding previously identified pathway-associated thromboembolic complications.

TNX-1500, a crystallizable fragment-modified anti-CD154 antibody, prolongs nonhuman primate cardiac allograft survival.

Blockade of the CD40/CD154 T cell costimulation pathway is a promising approach to supplement or replace current clinical immunosuppression in solid organ transplantation. We evaluated the tolerability and activity of a novel humanized anti-CD154 monoclonal antibody, TNX-1500 (TNX), in a nonhuman primate heterotopic cardiac allogeneic (allo) transplant model. TNX-1500 contains a rupluzimab fragment antigen-binding region and an immunoglobin G4 crystallizable fragment region engineered to reduce binding to the crystallizable fragment gamma receptor IIa and associated risks of thrombosis. Recipients were treated for 6 months with standard-dose TNX (sTNX) monotherapy, low-dose TNX monotherapy (loTNX), or loTNX with mycophenolate mofetil (MMF) (loTNX + MMF). Results were compared with historical data using chimeric humanized 5c8 monotherapy dosed as for loTNX but discontinued at 3 months. Median survival time was similar for humanized 5c8 and both loTNX groups, but significantly longer with sTNX (>265 days) than with loTNX (99 days) or loTNX + MMF (88 days) (P < 0.05 for both comparisons against sTNX). Standard-dose TNX prevented antidonor alloantibody elaboration, inhibited chronic rejection, and was associated with a significantly reduced effector T cells/regulatory T cells ratio relative to loTNX with MMF. No thrombotic complications were observed. This study demonstrated that TNX was well tolerated, prolongs allograft survival, and prevents alloantibody production and cardiac allograft vasculopathy in a stringent preclinical nonhuman primate heart allotransplant model.

Single Dose of Recombinant Chimeric Horsepox Virus (TNX-801) Vaccination Protects Macaques from Lethal Monkeypox Challenge.

The ongoing global Monkeypox outbreak that started in the spring of 2022 has reinforced the importance of protecting the population using live virus vaccines based on the vaccinia virus (VACV). Smallpox also remains a biothreat and although some U.S. military personnel are immunized with VACV, safety concerns limit its use in other vulnerable groups. Consequently, there is a need for an effective and safer, single dose, live replicating vaccine against both viruses. One potential approach is to use the horsepox virus (HPXV) as a vaccine. Contemporary VACV shares a common ancestor with HPXV, which from the time of Edward Jenner and through the 19th century, was extensively used to vaccinate against smallpox. However, it is unknown if early HPXV-based vaccines exhibited different safety and efficacy profiles compared to modern VACV. A deeper understanding of HPXV as a vaccine platform may allow the construction of safer and more effective vaccines against the poxvirus family. In a proof-of-concept study, we vaccinated cynomolgus macaques with TNX-801, a recombinant chimeric horsepox virus (rcHPXV), and showed that the vaccine elicited protective immune responses against a lethal challenge with monkeypox virus (MPXV), strain Zaire. The vaccine was well tolerated and protected animals from the development of lesions and severe disease. These encouraging data support the further development of TNX-801.

Effect of increasing intraperitoneal infusion rates on bupropion hydrochloride-induced seizures in mice.

BACKGROUND: It is not known if there is a relationship between input rate and incidence of bupropion-induced seizures. This is important, since different controlled release formulations of bupropion release the active drug at different rates. METHODS: We investigated the effect of varying the intraperitoneal infusion rates of bupropion HCl 120 mg/kg, a known convulsive dose 50 (CD50), on the incidence and severity of bupropion-induced convulsions in the Swiss albino mice. A total of 69 mice, approximately 7 weeks of age, and weighing 21.0 to 29.1 g were randomly assigned to bupropion HCl 120 mg/kg treatment by intraperitoneal (IP) administration in 7 groups (9 to 10 animals per group). Bupropion HCl was infused through a surgically implanted IP dosing catheter with infusions in each group of 0 min, 15 min, 30 min, 60 min, 90 min, 120 min, and 240 min. The number, time of onset, duration and the intensity of the convulsions or absence of convulsions were recorded. RESULTS: The results showed that IP administration of bupropion HCl 120 mg/kg by bolus injection induced convulsions in 6 out of 10 mice (60% of convulsing mice) in group 1. Logistic regression analysis revealed that infusion time was significant (p = 0.0004; odds ratio = 0.974) and increasing the IP infusion time of bupropion HCl 120 mg/kg was associated with a 91% reduced odds of convulsions at infusion times of 15 to 90 min compared to bolus injection. Further increase in infusion time resulted in further reduction in the odds of convulsions to 99.8% reduction at 240 min. CONCLUSION: In conclusion, the demonstration of an inverse relationship between infusion time of a fixed and convulsive dose of bupropion and the risk of convulsions in a prospective study is novel.

Convulsive liability of bupropion hydrochloride metabolites in Swiss albino mice.

BACKGROUND: It is known that following chronic dosing with bupropion HCl active metabolites are present in plasma at levels that are several times higher than that of the parent drug, but the possible convulsive effects of the major metabolites are not known. METHODS: We investigated the convulsive liability and dose-response of the three major bupropion metabolites following intraperitoneal administration of single doses in female Swiss albino mice, namely erythrohydrobupropion HCl, threohydrobupropion HCl, and hydroxybupropion HCl. We compared these to bupropion HCl. The actual doses of the metabolites administered to mice (n = 120; 10 per dose group) were equimolar equivalents of bupropion HCl 25, 50 and 75 mg/kg. Post treatment, all animals were observed continuously for 2 h during which the number, time of onset, duration and intensity of convulsions were recorded. The primary outcome variable was the percentage of mice in each group who had a convulsion at each dose. Other outcome measures were the time to onset of convulsions, mean convulsions per mouse, and the duration and intensity of convulsions. RESULTS: All metabolites were associated with a greater percentage of seizures compared to bupropion, but the percentage of convulsions differed between metabolites. Hydroxybupropion HCl treatment induced the largest percentage of convulsing mice (100% at both 50 and 75 mg/kg) followed by threohydrobupropion HCl (50% and 100%), and then erythrohydrobupropion HCl (10% and 90%), compared to bupropion HCl (0% and 10%). Probit analysis also revealed the dose-response curves were significantly different (p < 0.0001) with CD50 values of 35, 50, 61 and 82 mg/kg, respectively for the four different treatments. Cox proportional hazards model results showed that bupropion HCl, erythrohydrobupropion HCl, and threohydrobupropion HCl were significantly less likely to induce convulsions within the 2-h post treatment observation period compared to hydroxybupropion HCl. The mean convulsions per mouse also showed the same dose-dependent and metabolite-dependent trends. CONCLUSION: The demonstration of the dose-dependent and metabolite-dependent convulsive effects of bupropion metabolites is a novelty.

Alcohol significantly lowers the seizure threshold in mice when co-administered with bupropion hydrochloride.

BACKGROUND: Bupropion HCl is a widely used antidepressant that is known to cause seizures in a dose-dependent manner. Many patients taking antidepressants will consume alcohol, even when advised not to. Previous studies have not shown any interactions between bupropion HCl and alcohol. However, there have been no previous studies examining possible changes in seizure threshold induced by a combination of alcohol and bupropion HCl. METHODS: Experimentally naïve female Swiss albino mice (10 per group) received either single doses of bupropion HCl (ranging from 100 mg/kg to 120 mg/kg) or vehicle (0.9% NaCl) by intraperitoneal (IP) injection in a dose volume of 10 ml/kg, and single-dose ethanol alone (2.5 g/kg), or vehicle, 5 min prior to bupropion dosing. The presence or absence of seizures, the number of seizures, the onset, duration and the intensity of seizures were all recorded for 5 h following the administration of ethanol. RESULTS: The results show that administration of IP bupropion HCl alone induced seizures in mice in a dose-dependent manner, with the 120 mg/kg dose having the largest effect. The percentage of convulsing mice were 0%, 20%, 30% and 60% in the 0 (vehicle), 100, 110, and 120 mg/kg dose groups, respectively. Pretreatment with ethanol produced a larger bupropion HCl-induced convulsive effect at all the doses (70% each at 100, 110 and 120 mg/kg) and a 10% effect in the ethanol + vehicle only group. The convulsive dose of bupropion HCl required to induce seizures in 50% of mice (CD50), was 116.72 mg/kg for bupropion HCl alone (CI: 107.95, 126.20) and 89.40 mg/kg for ethanol/bupropion HCl (CI: 64.92, 123.10). CONCLUSION: These results show that in mice alcohol lowers the seizure threshold for bupropion-induced seizures. Clinical implications are firstly that there may be an increased risk of seizures in patients consuming alcohol, and secondly that formulations that can release bupropion more readily in alcohol may present additional risks to patients.