ST Pharm shifts focus to SmartCap supply biz after successful phase 1 Covid-19 vaccine study

ST Pharm has demonstrated the safety and immunogenicity of its Covid-19 vaccine candidate STP2104.

However, ST Pharm decided to expand its SmartCap supply business by making the most of STP2104 instead of continuing the vaccine’s clinical trials using the ancestral virus spike protein as an antigen, given the virus circulating in the current endemic situation is the Omicron variant JN.1.

ST Pharm said so in a public notice on Monday, disclosing the phase 1 clinical trial results of its mRNA-LNP-based Covid-19 vaccine candidate STP2104.

The phase 1 trial was an open-label, dose-escalating, multicenter clinical trial conducted in Korea and South Africa to evaluate the safety and immunogenicity of STP2104, a vaccine to prevent Covid-19 in healthy adults.

Researchers divided 30 subjects into two arms of 15 to receive two escalating doses of STP2104 at 25 μg/mRNA and 50 μg/mRNA to determine safety and immunogenicity.

Evaluation of the distribution of immune antibody titers at 28 days after the second dose of STP2104 in PPS1 subjects showed that the proportion of subjects with high antibody titers at 28 days after the second dose was slightly higher in the high dose (50 μg) than in the low dose (25 μg).

Considering the titer ranges < 775.6620, ≥ 775.6620, ≥ 1341.9979, and ≥ 2101.6012 IU/mL, the number of subjects in these ranges was four, eight, six, and three in the low dose group, respectively, and two, 11, seven, and four in the high dose group.

That was also true when considering the titer ranges < 1137.1153, ≥ 1137.1153, ≥ 2254.4413, and ≥ 2923.9413 by PRNT50, with three, nine, four, and two subjects in the low dose group, and three, 10, nine, nine, and five subjects in the high dose group.

When the distribution of binding antibody titers was evaluated on day 28 following the second dose of STP2104 in PPS1 subjects, the share of subjects with high binding antibody titers was the same in both comparator arms.

When considering the titer range < 250.0000 or ≥ 250.0000 U/mL, the number of subjects in this range was 0 and 12 in the low-dose arm and 0 and 13 in the high-dose arm. This indicates there was no difference in the proportion of subjects with high-binding antibody titers on day 28 after the second dose.

IFN-γ ELISpot assays were performed in PPS1 subjects, and for peptide 1, a slight decrease was observed from day 28 post-dose 1 to day seven post-dose 2, with mean (SD) values of 30.8 (55.9) and 30.4 (29.0). For peptide 2, about a two-fold increase was observed at 28 days post-dose, with peak spot/cell counts observed at 28 days post-dose.

Mean values in the high-dose group increased about 1.5- to four-fold from baseline to 28 days post-dose 1, with a further increase (generally less than two-fold) at seven days post-dose 2, and then decreased about two-fold at 28 days post-dose 2 (remaining about 0.5- to 3-fold higher than baseline). Peak spot/cell counts were observed at seven days post-second dose.

Intracellular cytokine staining (ICS) analysis showed no clear trend between vaccination and Th1/Th2 ratio over time for PPS1 subjects. In both PPS1 and FAS, there was no significant trend between vaccination over time and the parameters assessed.

“Four weeks after the second dose, STP2104 demonstrated neutralizing antibody titers of 1306 and 2285 at the low (25 μg/dose) and high (50 μg/dose) doses, representing 20.8- and 24.3-fold increases from pre-dose,” ST Pharm said. “It is therefore considered to be effective.”

According to ST Pharm, the phase 1 safety evaluation showed no serious adverse events, most of which were mild or localized. One Adverse Event of Special Interest (AESI) was reported, which was Grade 1 (mild) and did not require any action.

“STP2104 is equipped with SmartCap, an mRNA platform technology developed by ST Pharm, and is the only capping that has secured safety and immunogenicity through human clinical data besides competitor capping,” a company official said. “We expect that securing clinical data will open up various business partnership opportunities, such as SmartCap supply and L/O, in the future, as we signed a SmartCap supply agreement with global mRNA equipment manufacturer Quantoom Biosciences.”

The official also revealed the company’s plans.

“The SARS coronavirus currently spreading globally under the endemic situation is the Omicron variant JN.1, not the ancestral virus,” the official said. “Instead of conducting late-stage clinical trials with STP2104, which used the ancestral virus spike protein as an antigen, we would like to focus on developing an mRNA vaccine against the JN.1 variant if necessary.”