LONDON, UK — September 11, 2026

Persica Pharmaceuticals Limited published a new methodological analysis examining the sensitivity of microbiology techniques used in studies investigating bacterial presence in spinal discs, providing additional support for the scientific rationale behind PP353, its targeted, non-opioid treatment for vertebrogenic lumbar back pain (vLBP). The scoping review evaluated 22 published culture-based disc microbiology studies and identified substantial differences in the ability of individual methods to detect low levels of bacteria in disc tissue. According to the analysis, studies using good microbiology practices consistently detected low-bioburden infection in approximately 50% of evaluated discs, with around 80% of detected infections attributed to Cutibacterium acnes. Persica said the findings may help explain divergent results across the published literature and strengthen the rationale for investigating low-grade bacterial infection as a contributor to vLBP and Modic changes.

Assay Sensitivity May Explain Divergent Disc Microbiology Results

The analysis highlights assay sensitivity as a potentially important factor in interpreting published disc microbiology findings. Persica reported that low-sensitivity approaches may detect bacteria in only approximately 11% of samples that would otherwise be identified as positive using higher-sensitivity methods. In published series involving surgically obtained disc samples, low-sensitivity methods would also have quantified infection in less than 1% of examined samples. The company argues that these differences suggest that negative microbiology findings may sometimes reflect methodological limitations rather than a complete absence of bacteria. Cutibacterium acnes, which accounted for the majority of infections identified in higher-sensitivity studies, is already documented as a cause of low-bioburden infection in other human diseases, including infections associated with joint replacement and bacterial endocarditis. The manuscript has been submitted to the European Spine Journal and is available through its preprint server, providing a methodological basis for further discussion of bacterial involvement in disc-related disease.

PP353 Builds on Phase 1b Clinical Evidence

Persica’s lead candidate PP353 is designed to directly target the potential infectious component of vertebrogenic lumbar back pain. The investigational therapy is a targeted intradiscal antibiotic intended to be delivered directly to the site of disease in patients with vLBP and Modic changes, rather than relying on systemic treatment. In the randomized, double-blind, sham-controlled Phase 1b MODIC study involving 40 participants, PP353 demonstrated statistically significant and clinically meaningful improvements in pain and disability that remained durable through 12 months. More than 60% of treated patients achieved at least a 50% reduction in pain, while the study also reported decreased use of pain medication, including opioids. The findings, published in The Lancet eClinicalMedicine in February 2026, provide the clinical foundation for Persica’s continued development strategy. The latest microbiology analysis is intended to complement those clinical findings by strengthening the biological hypothesis underlying PP353.

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Persica Seeks Partners for Registrational Development

The new publication strengthens Persica Pharmaceuticals’ efforts to advance PP353 toward a registrational development program for patients with vLBP associated with Modic changes. The company estimates that this patient population represents approximately 15% of chronic low back pain patients, while current treatment approaches frequently focus on managing symptoms rather than addressing a potential underlying cause. PP353 is designed as a potential disease-modifying, non-opioid approach that directly targets the disc through intradiscal delivery. Persica is continuing discussions with potential strategic partners and investors to support the registrational program required to advance PP353 into Phase 3 trials. The combination of the Phase 1b clinical results and the newly published microbiology analysis provides the company with both clinical and mechanistic evidence as it seeks to define the next stage of development. Persica’s strategy now centers on translating the PP353 hypothesis into larger registrational studies and potentially establishing a targeted alternative to long-term analgesic treatment for vLBP.

Source: Persica Pharmaceuticals press release