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TNX-801 Mpox Vaccine Description

TNX-801 is a vaccine candidate that Tonix Pharmaceuticals Holding Corp. developed to protect humans against mpox and smallpox infection. TNX-801 was created as part of a research collaboration between Tonix and Professor David Evans, Ph.D., and Ryan Noyce, Ph.D., the Department of Cell Biology, University of Alberta. TNX-801 is a live virus vaccine based on synthesized horsepox, the sequence of the 1976 natural isolate Mongolian horsepox clone MNR-763. Molecular analysis of DNA sequences suggests that TNX-801 is closer than modern smallpox vaccines to the vaccine discovered and disseminated by Dr. Edward Jenner in 1798.

In July 2022, the Company Announced a collaboration with the Kenya Medical Research Institute (KEMRI) to seek regulatory approval for conducting a Phase 1 clinical study in Kenya to develop TNX-801. On November 9, 2022, the company gave a presentation on TNX-801 for Smallpox and Mpox.   On December 1, 2022, the company gave a Presentation at the World Vaccine & Immunotherapy Congress.

On November 13, 2024, Tonix announced the publication of a paper entitled, “Recombinant Chimeric Horsepox Virus (TNX-801) is Attenuated Relative to Vaccinia Virus Strains in Both In Vitro and In Vivo Models,” in the peer-reviewed journal mSphere. The publication presents data demonstrating that TNX‐801 is less virulent than 20th-century vaccinia vaccines in immune-compromised mice.

Tonix is a clinical-stage biopharmaceutical company focused on discovering, licensing, acquiring, and developing therapeutics to treat and prevent human disease and alleviate suffering.

Recombinant Pox Virus Platform

Horsepox virus and vaccines based on its use as a vector are live replicating viruses that elicit strong immune responses. Live replicating orthopoxviruses, like vaccinia or horsepox, can be engineered to express foreign genes and have been exploited as platforms for vaccine development because they possess (1) large packaging capacity for exogenous DNA inserts, (2) precise virus-specific control of exogenous gene insert an expression, (3) lack of persistence or genomic integration in the host, (4) strong immunogenicity as a vaccine, (5) ability to rapidly generate vector/insert constructs, (6) manufacturable at scale, and (7) ability to provide direct antigen presentation. Relative to vaccinia, horsepox has substantially decreased virulence in mice2. Horsepox-based vaccines are designed to be single-dose, vial-sparing vaccines manufactured using conventional cell culture systems, with the potential for mass-scale production and packaging in multi-dose vials. 

TNX-801 News

November 13, 2024 - “Addressing the new Clade Ib mpox outbreak and the ongoing spread of Clade IIb mpox may require a single dose mpox vaccine that provides durable protection,” said Seth Lederman, M.D., Chief Executive Officer of Tonix Pharmaceuticals.

December 1, 2022 - Tonix Pharmaceuticals Holding Corp. announced that Seth Lederman, M.D., CEO of Tonix Pharmaceuticals, presented data from the Company’s TNX-801 smallpox and monkeypox vaccine development program in an oral presentation. “TNX-801 is a live virus vaccine that we believe is closer to the smallpox vaccines used in the U.S. and Europe before 1900 than the modern vaccinia smallpox vaccines. TNX-801 has reduced virulence in animals, and we believe it has the potential for widespread use to protect against monkeypox,” said Seth Lederman, M.D., President and CEO.

TNX-801 Clinical Trials

Tonix Pharmaceuticals Holding Corp. (Nasdaq: TNXP) announced a collaboration with the Kenya Medical Research Institute (KEMRI) to plan, seek regulatory approval, and conduct a Phase 1 clinical study in Kenya to develop TNX-801 as a vaccine to protect against monkeypox and smallpox. The study is expected to start in the first half of 2023.

“KEMRI is excited to plan this clinical trial with Tonix and ultimately to lead the trial,” said Professor Samuel Kariuki, Director General and CEO of KEMRI. “Monkeypox has spread in Central and West Africa, and there’s a concern that we could begin seeing cases in Eastern and Central Africa or from foreign travelers. Recently, monkeypox has been reported in over 30 countries outside of Africa that were not endemic to the monkeypox virus. We are grateful that Tonix is committed to sponsoring clinical studies and making TNX-801 available for this important problem.”

CAPVAXIVE® Pneumococcal 21-valent Conjugate Vaccine Clinical Trials, Dosage, Indication, Side Effects

Merck's CAPVAXIVE® (V116) (Pneumococcal 21-valent Conjugate Vaccine (PVC21) prevents invasive pneumococcal disease (IPD) and pneumococcal pneumonia in adults. CAPVAXIVE addresses the serotypes that create adult pneumococcal disease, including eight unique serotypes: 15A, 15C, 16F, 23A, 23B, 24F, 31, and 35B. CAPVAXIVE utilizes the PeliCRM197® carrier protein, which helps enhance antigen immunogenicity in conjugate vaccines.

On June 17, 2024, the U.S. Food and Drug Administration (FDA) approved CAPVAXIVE (STN: BLA 125814/0), a vaccine specifically designed for adults, covering serotypes responsible for approximately 84% of invasive pneumococcal disease in adults 50 years and older. Across four Phase 3 studies, CAPVAXIVE demonstrated robust immune responses in vaccine-naïve and vaccine-experienced adult populations. CAPVAXIVE was approved in Canada in July 2024 and in Australia in January 2025.

On January 30, 2025, the Committee for Medicinal Products for Human Use of the European Medicines Agency (EMA) recommended the approval of CAPVAXIVE for adults 18 and older. On March 26, 2025, Merck announced that the EMA approved CAPVAXIE in all 27 European Union (EU) member states, including Iceland, Liechtenstein, and Norway.

On October 16, 2024, key findings from the STRIDE-8 trial included: CAPVAXIVE was immunogenic for all 21 serotypes included in the vaccine, as measured by serotype-specific OPA geometric mean titers (GMTs) (primary immunogenicity objective) and immunoglobulin G geometric mean concentrations (GMCs) (secondary immunogenicity objective) at Day 30; Immune responses elicited by CAPVAXIVE were comparable to PCV15 followed by PPSV23 for the 13 common serotypes and higher for the eight serotypes unique to CAPVAXIVE, as measured by serotype-specific OPA GMTs and IgG GMCs 30 days post-vaccination; The proportions of participants with adverse events (AEs), including injection-site, systemic, and vaccine-related AEs, were numerically lower in the V116 + placebo group than in the PCV15 + PPSV23 group.

Merck, known as MSD outside the United States and Canada, is united around a purpose: We use the power of cutting-edge science to save and improve lives worldwide. For more than four decades, Merck has been at the forefront of pneumococcal disease prevention through vaccination and remains committed to protecting people of all ages from this disease.

CAPVAXIVE Vaccine U.S. CDC ACIP

The U.S. Centers for Disease Control and Prevention (CDC) Advisory Committee on Immunization Practices (ACIP) Work Group decided on October 23, 2024, to lower the age-based recommendation to include adults 50-64 years. The ACIP met on June 27, 2024, and reviewed these presentations: Economic analysis and public health impact of PCV21 use in adults, Mr. C Stoecker; Summary of three economic studies on the use of 21-valent pneumococcal conjugate vaccine (PCV21) among adults in the U.S.; Andrew J. Leidner, PhD; Summary of WG Interpretation of EtR and policy options on PCV21 use in adults and clinical guidance for implementation, Dr. M Kobayashi on February 29, 2024. Heather Platt, M.D., presented Key Results from the Phase 3 Clinical Development Program, which include, but are not limited to the following: V116 elicits robust immune responses to all 21 serotypes contained in the vaccine; is noninferior to PCV20 for all common serotypes and superior to PCV20 for 10 of 11 serotypes unique to V116 in pneumococcal vaccine-naïve adults ≥50 years of age; is immunogenic in pneumococcal vaccine experienced adults, regardless of the prior vaccine received; is immunogenic when administered concomitantly with inactivated influenza vaccine; and V116 is well-tolerated with a safety profile generally comparable to currently licensed pneumococcal vaccines. The initial assessment by the ACIP Work Group suggested that V116 provides broader serotype coverage than currently recommended vaccines for adults aged 65 and older or immunocompromised adults. Miwako Kobayashi, M.D., presented the Work Group's proposed policy questions on lowering the age-based recommendation for pneumococcal vaccination to include adults aged 50-64. The ACIP is expected to vote in an upcoming meeting on whether V116 should be recommended as a pneumococcal vaccination option for U.S. adults. CDC recommendations follow FDA approval.

CAPVAXIVE Vaccine Indication

V116 is designed to be administered as a single dose to help prevent invasive pneumococcal disease and pneumonia in adults. Over 150,000 adults are hospitalized with pneumococcal pneumonia each year in the U.S. The serotypes covered by V116 are responsible for approximately 83% of invasive pneumococcal disease in individuals 65 and older. Pneumococcal disease is an infection caused by the bacterium Streptococcus pneumoniae. There are more than 100 types (serotypes) of pneumococcal bacteria.

CAPVAXIVEV Vaccine Availability

As of 2025, CAPVAXIVE has been approved by the U.S. FDA (STN: BL 125814/0) and approved in Canada, Australia, and Europe.

CAPVAXIVE V116 Vaccine News

April 24, 2025 - Merck announced that CAPVAXIVEW produced $107 million in sales, representing continued uptake since its launch in the U.S. in the third quarter of 2024.

March 26, 2025 - Dr. Paula Annunziato, senior vice president, infectious diseases and vaccines, Global Clinical Development, Merck Research Laboratories, stated, "We are proud to bring CAPVAXIVE to adults in Europe who may benefit from its broad protection and are eager to continue working with regulatory authorities to expand CAPVAXIVE availability worldwide."

January 31, 2025—Dr. Paula Annunziato, senior vice president of infectious diseases and vaccines, Global Clinical Development, Merck Research Laboratories, commented in a press release, "This positive opinion is yet another testament to the clinical profile of CAPVAXIVE and brings us a step closer to helping protect adults in the EU against pneumococcal disease. Invasive pneumococcal disease can lead to serious consequences, including hospitalization, organ damage, and even death. We are pleased with the CHMP recommendation and look forward to the European Commission's decision."

October 16, 2024 - "Adults with chronic medical conditions, such as kidney disease or diabetes, are particularly vulnerable to invasive pneumococcal disease, which may increase their risk of severe illness," said Dr. Walter Orenstein, professor emeritus of medicine, epidemiology, global health and pediatrics at Emory University and member of Merck's Scientific Advisory Committee.

June 21, 2024 - Nature published a news brief - FDA approves 21-valent pneumococcal vaccine.

June 17, 2024: Dr. Walter Orenstein, professor emeritus of medicine, epidemiology, global health, and pediatrics at Emory University and member of Merck's Scientific Advisory Committee, stated, "CAPVAXIVE is designed to include the serotypes that cause the majority of invasive pneumococcal disease in adults, helping to protect them against invasive pneumococcal disease and pneumococcal pneumonia."

March 19, 2024 - "The extensive data presented this week reaffirms our confidence in the potential clinical value V116 could provide to a range of adult populations," said Dr. Eliav Barr, senior vice president, head of global clinical development and chief medical officer, Merck Research Laboratories, in a press release. "We are encouraged by the results of these studies showing that V116 has generated immune responses to the serotypes responsible for most adult invasive pneumococcal disease."

February 29, 2024 - James Loehr, MD, led a U.S. CDC vaccine committee review of V116.

July 28, 2022 - Merck presented positive results from the Phase 1/2 study for V116, Merck's investigational Pneumococcal 21-Valent Conjugate Vaccine designed to target serotypes that account for 85% of all invasive pneumococcal diseases in U.S. adults 65 years and older as of 2019, and enrolled the first patient into the Phase 3 STRIDE-3 trial evaluating V116 in vaccine-naïve adults. V116 contains eight serotypes not included in any currently licensed pneumococcal vaccine.

June 21, 2022 - Merck announced the presentation of positive results from the Phase 1/2 study, V116-001, evaluating the safety, tolerability, and immunogenicity of V116, the company's investigational 21-valent PCV, in pneumococcal vaccine-naïve adults 18-49 years of age (Phase 1) and 50 years of age and older (Phase 2).

April 14, 2022 - V116, Merck's investigational 21-valent pneumococcal conjugate vaccine, received Breakthrough Therapy Designation from the U.S. Food and Drug Administration (FDA) for the prevention of IPD and pneumococcal pneumonia caused by Streptococcus pneumoniae serotypes 3, 6A/C, 7F, 8, 9N, 10A, 11A, 12F, 15A, 15B/C, 16F, 17F, 19A, 20, 22F, 23A, 23B, 24F, 31, 33F, 35B in adults 18 years of age and older.

V116 Vaccine Clinical Trials

Merck's 21-valent PCV has been in clinical trials since 2019. Multiple Phase 3 trials of V116 were initiated within the last 12 months, including STRIDE-3 (NCT05425732), STRIDE-6 (NCT05420961), STRIDE-7 (NCT05393037), STRIDE-4 (NCT05464420), STRIDE-5 (NCT05526716), and STRIDE-8 (NCT05696080).

On March 19, 2024, Merck announced across the clinical studies presented at the 13th Meeting of the International Society of Pneumonia and Pneumococcal Diseases, V116 was shown to be immunogenic for all 21 serotypes covered by the vaccine in a variety of adult populations, including those who had not previously received a pneumococcal vaccine (pneumococcal vaccine-naïve), those who had previously received a pneumococcal vaccine (pneumococcal vaccine-experienced) and those with an increased risk of pneumococcal disease, including people living with HIV. V116 also elicited higher immune responses than the studied comparators for the serotypes unique to V116 in all STRIDE studies presented at this meeting. In addition to Phase 3 clinical data on V116, Merck also presented preliminary data from the real-world evidence study ((Abstract #308)) on March 19, 2024, Pneumococcal Pneumonia Epidemiology, Urine Serotyping, and Mental Outcomes (PNEUMO), which found that among 2,065 adults 50 years of age and older hospitalized with community-acquired pneumonia between 2018 and 2022, 242 pneumococcal serotypes were detected. Of these serotypes, approximately 84% were covered by V116. About 25% of the detected serotypes were covered only by V116, not PCV15 or PCV20.

Data from STRIDE-3 Sub-group (Abstract #379) - The sub-group analysis of the pivotal STRIDE-3 (NCT05425732) trial evaluated immunogenicity in adults 50 years of age and older who had not previously received a pneumococcal vaccine (Cohort 1) by age groups (50–64, 65–74 and 75–84 years) (n=2,362). Results found that V116 was immunogenic for all 21 vaccine serotypes across the studied age sub-groups, as assessed by serotype-specific OPA GMTs 30 days post-vaccination. There was a slight downward trend in immune responses among adults aged 65–74 and those 75 years and older, compared to adults in other age groups. V116 had a safety profile comparable to PCV20. Results from the STRIDE-3 trial were presented at the World Vaccine Congress West Coast in November 2023.

Data from STRIDE-6 and the STRIDE-6 Sub-group (Abstracts #353 and #520) - STRIDE-6 (NCT05420961) is a Phase 3 trial investigating V116 in adults 50 years of age and older who had previously received a pneumococcal vaccine at least one year prior (n = 712). Participants were enrolled based on previous pneumococcal vaccination with PPSV23, PCV15, PCV13 (pneumococcal 13-valent conjugate vaccine), PPSV23+PCV13, PCV13+PPSV23 or PCV15+PPSV23, and received either V116, PCV15 or PPSV23.

Results showed that V116 was immunogenic across all cohorts, as assessed by OPA GMTs 30 days post-vaccination, and that V116 elicited comparable immune responses to the serotypes also covered by PCV15 and PPSV23, as well as higher immune responses for the serotypes covered only by V116. A STRIDE-6 sub-group analysis evaluating immunogenicity across all cohorts by time since prior pneumococcal vaccination found that V116 elicited comparable immune responses regardless of time since prior pneumococcal vaccination, including more than ten years post-vaccination with PPSV23 (n=56), and 5–9 years post-vaccination with either PPSV23 or other pneumococcal vaccines (n=208). In this study, V116 had a safety profile comparable to PCV15 and PPSV23.

Data from STRIDE-7 (Abstract #1093) - STRIDE-7 (NCT05393037) is a Phase 3, double-blind study of V116 in adults living with HIV (n=304). Results showed that V116 was immunogenic for all serotypes covered by the vaccine, as assessed by OPA GMTs and IgG GMCs 30 days post-vaccination. V116 elicited comparable immune responses to the comparator, PCV15+PPSV23, for all 13 shared serotypes and higher immune responses for the eight serotypes covered only by V116. Fewer participants experienced adverse events (AEs) with V116 (71.6%) compared with PCV15+PPSV23 (91%), primarily due to fewer injection-site AEs.

Data from STRIDE-9 (Abstract #1085) - STRIDE-9 (NCT05633992) is a Phase 3, randomized, double-blind, active-comparator-controlled study that investigated V116 in Japanese adults aged 65 years and older who had not previously received a pneumococcal vaccine (n = 450). Serotype-specific OPA responses were measured at baseline and 30 days post-vaccination, and the results demonstrated that V116 elicited non-inferior immune reactions for the 12 serotypes shared with PPSV23 and serotype 15B (which is included in PPSV23 but not in V116). V116 also elicited higher immune responses for the serotypes covered only by V116 and not by PPSV23. V116 also had a comparable safety profile to PPSV23.

Data from PNEUMO U.S. Serotype Distribution Study (Abstract #308) - The PNEUMO U.S. study evaluated pneumococcal serotype distribution among adults 50 years of age and older hospitalized with community-acquired pneumonia (n=2,065), one of the non-invasive forms of pneumococcal disease, between 2018 and 2022 in three hospitals in Tennessee and Georgia. Urine samples from patients were evaluated for antigens from 30 pneumococcal serotypes using novel serotype-specific urinary antigen detection (SSUAD) assays (all serotypes in PCV15, PCV20, and V116 are included except 15B). Among the 242 serotypes detected by SSUAD assays, approximately 84% were covered by V116, compared to approximately 64% covered by PCV20. One-fourth (approximately 25%) of the detected serotypes were covered by V116 only and not by PCV15 or PCV20.

Additional Clinical Study Results Presented at ISPPD (Abstract #382 and #355) - Data from Phase 3 clinical studies STRIDE-4 (NCT05464420) and STRIDE-5 (NCT05526716) were also presented at ISPPD.

SKYCovione™ COVID-19 Vaccine

SK bioscience SKYCovione™ (SKYCovion™, GBP510) is a recombinant protein-based vaccine made of proteins that form tiny particles studded with fragments of the pandemic SARS-CoV-2 coronavirus. These nanoparticles were designed by scientists at the University of Washington School of Medicine (UW of Medicine) and advanced into clinical trials by SK bioscience and  GlaxoSmithKline (GSK) with financial support from the Coalition for Epidemic Preparedness Innovations. In addition, SKYCovione includes GSK's pandemic adjuvant, AS03, which helps strengthen the immune response to the vaccine.

The vaccine consists of GBP510 with the AS03 adjuvant. GBP510 is a self-assembling two-component protein nanoparticle that displays 60 copies of the receptor-binding domain (RBD) of SARS-CoV-2 Spike. The nanoparticle component allows for the high-level multimeric display of the RBD antigen that enhances humoral immune responses even at lower doses. This platform also allows for efficient and straightforward adjustment of the vaccine to match variant strains of SARS-CoV-2 or other emergent pathogens by swapping out the target antigen displayed by the nanoparticle. In addition, the inclusion of AS03 may enable the use of lower doses of the protein antigen.

The Phase 3 clinical trial results showed that SKYCovion induced neutralizing antibody responses and had an acceptable safety and reactogenicity profile compared to the control vaccine, Vaxzevria™, used in the study. In addition, the extended phase I/II clinical trials showed a high immune response to the Omicron variant after a booster of SKYCovion. The clinical trial was conducted at 16 institutions, including the Korea National Institute of Health Vaccine Center, the International Vaccine Institute, and Korea University Guro Hospital.

The Korean Ministry of Food and Drug Safety approved SKYCovione for use on June 29, 2022, in individuals 18 years and older. In addition, the South Korean government has agreed to purchase 10 million doses for domestic use. On May 30, 2023, the UK's Medicines and Healthcare products Regulatory Agency (MHRA) granted Marketing Authorization for SK bioscience's COVID-19 vaccine SKYCovion™ as a primary series for strong immunization to prevent COVID-19 caused by SARS-CoV-2 in individuals 18 years of age and older. On June 19, 2023, SkyCovione received an Emergency Use Listing (EUL) from the World Health Organization (WHO). SKYCovione is the 12th COVID-19 vaccine granted an EUL by the WHO.

SKYCovion is the world's first vaccine developed using the RoseTTAFold, a software tool that uses deep learning to quickly and accurately predict protein structures from limited information. The RoseTTAFold was designed as a three-track neural network developed by the University of Washington.

SK bioscience is an innovative biopharmaceutical company committed to global pandemic preparedness through vaccine development and manufacturing to create more equitable access to vaccines.

SKYCovione Indication

SKYCovione is indicated to prevent the disease COVID-19 caused by the SARS-CoV-2 virus. When a person is given the vaccine, their immune system is expected to identify the nanoparticles containing parts of the spike protein as foreign and produce natural defenses - antibodies and T cells - against them. If, later on, the vaccinated person comes into contact with SARS-CoV-2, the immune system will recognize the spike protein on the virus and be prepared to attack it. The antibodies and immune cells can protect against COVID-19 by working together to kill the virus, prevent its entry into the body's cells, and destroy infected cells.

"This intramuscular vaccine was designed at the molecular level to present the immune system with a key part of the coronavirus spike protein. We know this part, called the receptor-binding domain, is targeted by the most potent antibodies," said Neil King, an assistant professor of biochemistry at UW Medicine and co-developer of the vaccine.

SKYCovion Booster

SK bioscience announced that SKYCovione had shown cross-neutralizing activity against Omicron variant BA.1 following booster vaccination administered ~7 months after the primary series. The results of the Phase I/II clinical trial, conducted with 81 healthy adults who received a booster dose of SKYCovione 7 months after the second dose of SKYCovione™, showed that the neutralizing antibody titers against the Omicron variant BA.1 were 25 times the titers right after the second dose, and 72 times the titers seven months after the second dose. 

SKYCovione News

June 19, 2023 - Jaeyong Ahn, CEO of SK bioscience said, "Based on the immunogenicity and safety profile, SKYCovione has become the first Korean vaccine to be granted to the WHO EUL. We will be committed to developing more vaccines to strengthen Korea's vaccine sovereignty and enable equitable access to the vaccine."

May 30, 2023 - Jaeyong Ahn, CEO of SK bioscience said in a press release, "We are delighted with the MHRA's authorization of Korea's first COVID-19 vaccine SKYCovion. This is the result of our commitment to protecting and promoting global public health. We are confident it will be the milestone to solidify our position in the global market amid the transition of the pandemic to the endemic phase."

August 18, 2022 - The EMA's human medicines committee began reviewing a conditional marketing authorization application for Skycovion, a vaccine to protect against COVID-19.

August 1, 2022 - SK bioscience announced that it had applied for a Conditional Marketing Authorization for SKYCovion to the European Medicines Agency.

July 29, 2022 - SK bioscience announced that it applied for a Conditional Marketing Authorization of the SKYCovion to the UK Medicines and Healthcare Products Regulatory Authority.

June 29, 2022 - The Seattle scientists behind the new vaccine sought to create a 'second-generation' COVID-19 vaccine that is safe, effective at low doses, simple to manufacture, and stable without deep freezing. These attributes could enable vaccination on a global scale by reaching people in areas with limited medical, transportation, and storage resources.

SKYCovione Clinical Trials

A Phase 3 clinical trial, Immunogenicity and Safety Study of SK SARS-CoV-2 Recombinant Nanoparticle Vaccine (GBP510) Adjuvanted With AS03 (COVID-19), compared the immunogenicity and safety of SKYCovione recombinant nanoparticle vaccine adjuvanted with AS03 (GBP510) to the Oxford/AstraZeneca vaccine Covishield/Vaxzevria in adults aged 18 years and older. The results indicated that SKYCovione elicits roughly three times more neutralizing antibodies than the Oxford/AstraZeneca vaccine Covishield/Vaxzevria. In these studies, SKYCovione or Covishield/Vaxzevria was administered twice with an interval of four weeks. In the Phase 3 trial, there were again no severe adverse reactions to the vaccine.

Phase 1/2 trial results announced by SK bioscience last November and posted as a preprint found that SKYCovione was safe and produced virus-neutralizing antibodies in all trial participants receiving the adjuvanted vaccine.