Results indicate potential best-in-class RSV+hMPV±PIV3 combination vaccines, with the potential ability to re-vaccinate individuals previously receiving approved RSV vaccines to restore and broaden protection --

-- Increases in neutralizing antibodies of approximately 6-8 fold for RSV, 6-9 fold for hMPV and 4 fold for PIV3 (≥10 fold increases in PIV3 PreF-specific antibodies) were observed --

-- Interim analysis from RSV re-vaccination trial demonstrates ≥60% higher trend in RSV neutralizing antibodies for Clover's RSV vaccine compared head-to-head versus AREXVY (GSK) in older adults previously receiving an initial dose of AREXVY --

-- Potential first-in-class RSV+hMPV±PIV3 combination vaccine candidates to advance to Phase II clinical trials in the first half of 2026 --

Clover Biopharmaceuticals, Ltd., a global commercial-stage biotechnology company committed to unleashing the power of innovative vaccines to save lives and improve health around the world,  announced positive preliminary data from two ongoing clinical trials evaluating the company's combination respiratory PreF vaccine candidates (RSV+hMPV±PIV3) leveraging its validated Trimer-Tag platform technology including:

• A Phase I trial in Australia evaluating SCB-1022 (RSV+hMPV) and SCB-1033 (RSV+hMPV+PIV3) combination vaccines compared head-to-head with SCB-1019 (RSV) in RSV vaccine-naïve older adults; and,
• A Phase I trial in the U.S. evaluating re-vaccination with SCB-1019 compared head-to-head versus AREXVY (GSK's RSV vaccine) in older adults previously receiving AREXVY at least 2 seasons prior to enrolling.

"We are pleased to announce positive Phase I clinical data indicating a potential best-in-class profile for our RSV+hMPV±PIV3 combination vaccine candidates, with the potential ability to re-vaccinate individuals previously receiving approved RSV vaccines to restore and broaden protection," said Joshua Liang, Chief Executive Officer & Board Director of Clover. "While currently approved protein-based RSV vaccines are safe & effective, critical gaps persist globally, including (1) the inability to prevent significant respiratory disease burden caused by other viruses related to RSV such as human metapneumovirus (hMPV) and parainfluenza virus type 3 (PIV3) and (2) the inability to re-vaccinate effectively when protection against RSV disease wanes. We look forward to advancing our RSV+hMPV±PIV3 combination vaccines into Phase II clinical trials in the first half of 2026 to strengthen our potential first-in-class and best-in-class profile." 

RSV+hMPV±PIV3 Combination Vaccines Phase I Trial (Australia): Preliminary Full Results

In an ongoing Phase I trial in Australia, older adults (60-85 years) were enrolled and randomized to receive either SCB-1022 (RSV+hMPV), SCB-1033 (RSV+hMPV+PIV3) or SCB-1019 (RSV) comparator. The study is assessing safety, reactogenicity and immunogenicity, with preliminary results from 144 participants (48 participants per vaccine group) at the selected dose levels summarized below:

• RSV Immune Responses: Geometric mean fold rises (GMFRs) of approximately 6-8 fold in RSV-A and RSV-B neutralizing antibodies (nAbs) at 28 days post-vaccination were observed for both SCB-1022 and SCB-1033, which were in-line with the SCB-1019 comparator (and also in-line with previous results from a separate clinical trial conducted by Clover comparing SCB-1019 head-to-head versus AREXVY).
  • No signs of immune interference on RSV nAb responses from the addition of hMPV and PIV3 PreF antigens in the RSV+hMPV±PIV3 combination vaccines were observed.
• hMPV Immune Responses: GMFRs of approximately 6-7 fold in hMPV-A nAbs and approximately 8-9 fold in hMPV-B nAbs were observed for both SCB-1022 and SCB-1033.
  
  
• PIV3 Immune Responses: GMFRs of approximately 4 fold in total PIV3 nAbs was observed for SCB-1033, along with ≥10 fold increases in PIV3 PreF-specific antibodies (against Site Ø and Site X) confirming that the PreF-specific antibody responses against PIV3 are likely at least in-line with responses observed for RSV and hMPV.
  • In participants with pre-existing baseline PIV3 nAb levels in the bottom 50^th percentile, GMFRs of approximately 6 fold in PIV3 nAbs was observed for SCB-1033, suggesting stronger responses in people who may be most at-risk for infection and disease.
  • PIV3 PreF-specific nAbs (such as Site Ø and Site X) can potently neutralize the PIV3 virus^[1], but unlike RSV and hMPV, the majority of pre-existing PIV3 nAbs at baseline are against the PIV3 HN protein (whereas levels of pre-existing PIV3 nAbs against the PIV3 PreF protein at baseline are low)^[2]. Therefore, a numerically lower increase in total PIV3 nAbs induced by SCB-1033 (containing PIV3 PreF antigen) – as compared to increases in RSV and hMPV nAbs – is expected.
• Safety and Reactogenicity: SCB-1022 and SCB-1033 were generally well-tolerated. Local and systemic AEs were generally mild for SCB-1022 and SCB-1033 and were comparable to SCB-1019, which had previously demonstrated significantly better tolerability than AREXVY in a separate trial. No vaccine related serious adverse events (SAEs), adverse events of special interest (AESIs), or AEs leading to discontinuation were observed for SCB-1022, SCB-1033 or SCB-1019.

Based on these positive Phase I results, Clover plans to advance SCB-1022 and SCB-1033 to Phase II clinical trials in the first half of 2026.

RSV Re-Vaccination Phase I Trial (U.S.): Preliminary Interim Analysis Results

Enrollment is ongoing in a Phase I trial in the U.S. in older adults (60-85 years) who previously received an initial dose of GSK's RSV vaccine (AREXVY) at least 2 seasons prior. Participants are being randomized to receive either a heterologous SCB-1019 (Clover RSV PreF) revaccination dose, a homologous AREXVY (GSK RSV PreF) revaccination dose or saline placebo. The study is assessing safety, reactogenicity and immunogenicity.

AREXVY homologous re-vaccination (when given at 2-3 years after the initial dose) has previously been reported to boost RSV nAbs only up to approximately 60-65% of the peak levels that were induced by the initial dose^[3], implying that an incremental approximately 1.5x higher response induced by SCB-1019 heterologous re-vaccination (if observed) compared to AREXVY homologous re-vaccination may be able restore peak levels of RSV nAbs and protection.

An interim analysis for immunogenicity in Clover's ongoing re-vaccination trial has been performed, and the preliminary results from 34 participants (16 participants receiving SCB-1019, 15 participants receiving AREXVY, 3 participants receiving saline placebo) are summarized below:

• RSV nAbs: SCB-1019 heterologous re-vaccination induced a 1.6-1.8x higher trend in GMFRs for RSV-A and RSV-B nAbs compared to AREXVY homologous re-vaccination, with approximately double the percentage of participants observing increases in RSV nAbs (≥2-fold):
  • GMFRs in RSV nAbs: Approximately 3.0-3.3 fold GMFRs in RSV-A and RSV-B nAbs were induced in participants receiving SCB-1019, as compared to 1.8-1.9 fold for AREXVY and no increases for placebo.
  • % of Participants with Increases in RSV nAbs: 69-75% of participants receiving SCB-1019 observed ≥2-fold increases in RSV-A and RSV-B nAbs, as compared to 33-40% for AREXVY and 0% for placebo.
  • Randomization and Baseline Characteristics: The randomization of participants included in this interim analysis was consistent, with baseline characteristics (such as baseline RSV nAb titers, participant age, re-vaccination interval) in the SCB-1019 and AREXVY groups being highly comparable. Baseline RSV nAb titers prior to re-vaccination in this study appeared to be approximately 2-3 fold higher than baseline nAb titers in RSV vaccine-naïve older adults from other clinical trials and is consistent with the previously reported results for AREXVY at 2-3 years following the initial dose^[3].

Given that more than 40% adults 60 years and older in the U.S. have previously received an protein-based RSV vaccine (comprising approximately 15 million doses)^[4], and clinical data to-date for currently approved RSV vaccines have not supported RSV re-vaccination policy recommendations despite waning efficacy observed after the initial dose, these preliminary clinical data from Clover's interim analysis suggest the potential for Clover's RSV+hMPV±PIV3 combination vaccine candidates to both restore protection against RSV and broaden protection to hMPV±PIV3 in this population.

Additional data from the ongoing RSV re-vaccination trial is expected by the first half of 2026.