Precision Biologics to Reveal Preclinical Efficacy of Novel Tumor-Specific ADC against multiple human cancer types at SITC 2025

BETHESDA, Md., Nov. 5, 2025 /PRNewswire/ -- Precision Biologics, Inc. announces in vitro and in vivo efficacy of its novel tumor-specific ADC (PB-vcMMAE-5) against human carcinomas expressing truncated core 2 O-glycans. Recent data for several human cancer types expressing truncated core 2 O-glycans will be presented in a poster at the Society for Immunotherapy of Cancer (SITC) Annual Meeting on November 7th, 2025, National Harbor, MD, USA. 

Poster title: In vitro and in vivo efficacy of the antibody-drug-conjugate (ADC) PB-vcMMAE-5 against human carcinoma expressing truncated core 2 O-glycans 

Presentation of the poster will be made in person on the following date and location: 

Friday, November 7th,  12:15pm – 1:45pm ET; & 5:35pm – 7pm ET 

Gaylord National Resort and Convention Center,  National Harbor, MD, USA 

Lower Level Atrium – Prince George's ABC 

Primary Category: Immuno-Conjugates and Chimeric Molecules 

Abstract Number: 949

BACKGROUND: 

Solid tumors remain largely unresponsive to immune checkpoint inhibitors, in part due to their ability to suppress the cytotoxic activity of immune cells infiltrating the tumor microenvironment. One of the disrupted pathways in these cancers is O-glycosylation, a feature particularly associated with cancer progression, metastasis, and poor prognosis.

One strategy to overcome resistance of solid tumor to immunotherapy is the employment of antibody-drug-conjugates (ADCs) selectively targeting cancer cells and not healthy tissues. We developed an ADC, designated PB-vcMMAE-5, composed of the following:

• The monoclonal antibody (mAb): We used PB-223, an innovative mAb developed through affinity maturation of clinical stage mAb NEO-102 (Ensituximab), a chimeric human IgG1 mAb that targets truncated core 2 O-glycans, specifically expressed by cancer cells and not by healthy tissues. PB-223 does not bind to normal tissues and it internalizes into human cancer cell lines expressing its target. 

• The payload: Monomethyl auristatin E (MMAE) was used as payload. MMAE is a potent antimitotic agent that inhibits cell division by blocking the polymerization of tubulin and is the most common ADC payload used to be linked to antibodies in clinical development for oncologic applications. 

• The linker: mc-vc-PABc was used as a cleavable linker. PB-223 was conjugated to the linker-payload through a cysteine-based conjugation method. 

The drug-to-antibody ratio (DAR) of PB-vcMMAE-5 is 3.92. 

Study presented at SITC Annual Meeting 2025 includes the following data:

• PB-223 specific binding to human tumor tissues by immunohistochemistry (IHC): PB-223 binds selectively to human tumor tissues and not to human normal tissue. PB-223 strongly reacted with colorectal, pancreatic, lung, prostate, and ovarian tumor tissues.

• In vitro  efficacy of PB-vcMMAE-5 against several human cancer cell lines: The in vitro cytotoxicity of PB-vc-MMAE-5 was evaluated in 9 human cancer cell lines, including prostate (PC-3, LnCAP), triple negative breast (HCC1937, MDA-MB-231), ER+,PR+,HER2+ breast (BT-474), squamous cell carcinoma of the lung (NCI-H226), ovarian (OV-90), colorectal (SW403), and pancreatic (CFPAC-1) cancer cell lines. This study shows that PB-vcMMAE-5 effectively killed all cell lines tested, with the highest percentage of killing observed against MDA-MB-231 (triple negative breast), LnCAP (prostate), OV-90 (ovarian), and NCI-H226 (lung) cancer cell lines.

In contrast, naked PB-223 mAb showed no killing in all cell lines tested.

• In vivo  safety of PB-vcMMAE-5 in mice: NOD-SCID mice bearing OV-90 (ovarian) xenografts were treated with weekly doses of PBS, MMAE alone, or PB-vc-MMAE-5 (1, 3, 6, or 9 mg/kg) for five weeks. Animal body weight was monitored regularly, twice a week, as an indirect measure of toxicity. The ADC PB-vcMMAE-5 was well tolerated in mice. No sign of distress and no loss of body weight were observed.
  No significant changes in body weight, blood parameters including hematology and clinical chemistry, nor pathological changes in the liver, spleen, brain, or heart of mice treated with efficacious doses of the ADC were observed compared with control groups. 

• In vivo  efficacy of PB-vcMMAE-5 in mice: The efficacy of the ADC PB-vcMMAE-5 was assessed in OV-90 (ovarian) subcutaneous xenograft model established in NOD-SCID mice. The ADC PB-vcMMAE-5 was administered intravenously at doses 1, 3, 6 or 9 mg/kg, once per week for five weeks. 
  On day 31 from the first ADC infusion, most alive mice were sacrificed, and tumors were excised for histological analysis using Ki-67 staining to assess proliferating viable tumor cells. To further assess systemic toxicity and prolonged efficacy, three mice each from the 6 and 9 mg/kg groups were followed to day 45. 
   
  Data presented in this study show that PB-vcMMAE-5 induced significant tumor growth inhibition compared to controls in a dose-dependent manner.

The highest tumor growth inhibition was observed at 6 and 9 mg/kg doses.

• In addition, analysis of tumors at day 45 showed absence of viable tumor cells and presence of tumor cells in necrosis, in mice treated with PB-vcMMAE-5 at 9 mg/kg. 

Findings from this study showed that PB-vcMMAE-5 can kill human cancer cells expressing PB-223's target, is not toxic in vivo in mice, and is highly effective in vivo at 9 mg/kg in NOD-SCID mice bearing human ovarian cancer. In addition, in a poster presented at AACR Annual Meeting 2025 we reported that PB-vcMMAE-5 is stable in human plasma. 

All these data suggest that PB-vcMMAE-5 has promising potential as a therapeutic option for a range of human malignancies expressing core 2 O-glycans.

The PDF of the poster will be available starting from November 5th, 2025, at the following link: 

https://precision-biologics.com/wp-content/uploads/SITC-2025-Abstract-949.pdf 

SOURCE Precision Biologics