Two posters showing new sets of preclinical data from Innate Pharma SA new, site-specific BTG-ADC conjugation technology, a rapid and versatile process appropriate for generating and testing various linkers and toxins such as pyrrolobenzodiazepine (PBD), in high-throughput screening, were presented during the World ADC Summit, being held in San Diego, October 26 – 29, 2014.
In the first poster, Site-specific conjugation by BTG improves the therapeutic index of ADC in vivo, scientists describe the in vitro and in vivo characterizations of antibody-drug conjugates uses novel site conjugation coupling technology. The technology uses Bacterial Transglutaminase (BTG) enzyme, which catalyses reactions between glutamine and lysine. BTG recognizes exclusively endogenous Q295 located in Fc region of aglycosylated IgG 
The technology aims to address the heterogeneity of the coupling between the antibody and the drug of interest, which affects the therapeutic efficacy of antibody conjugates. Using this technology, a single point mutation in the antibody’s heavy chain generates either two or four enzyme-recognition sites. Linkers have been optimized to couple quantitatively at these positions.
Using this technology, scientists have been able to create homogeneous ADCs with a drug-to-antibody ratio of exactly 2:1 or 4:1.
Innate’s novel technology was used to site-specifically conjugate derivatives of monomethyl auristatin E (MMAE) to the glutamine position 295 and 297 of cAC10, the parental antibody of brentuximab vedotin (Adcetris®; Seattle Genetics), one of the two reference ADCs approved by FDA, yielding to homogeneous BTG-ADC with a drug -to-antibody ratio or DAR of 4.
The researchers compared the BTG-ADC antibody-drug conjugates in vitro and in vivo to brentuximab. Using two different CD30+ cell lines (Karpas 299 and Rai-CD30+), they observed comparable EC50-values for in vitro cell toxicity for brentuximab and cAC10-based BTG-ADCs. In the BTG-ADCs, the scientists did not observe any DAR variations in vivo in rats over 15 days, and, compared to brentuximab there was a significant lower clearance of the total antibody.
Quantitative time-dependent in vivo biodistribution showed higher tumor uptake.
In the second poster, Versatility of Site-Specific Conjugation based on Bacterial Transglutaminase, scientists show the potential of BTG site specific conjugation for high-throughput screening of ADCs. Based on this research, the Innate scientists showed that their chemo-enzymatic approach, in addition to allowing conversion of virtually any IgG1 into a functional antibody-drug conjugate, also enables comparison of various antibodies, linker systems or cytotoxins. 
The scientists were able to effectively conjugate and evaluate in vivo cAC10 with various drugs, including MMAE, MMAF and PBD.
The key conclusion of these posters is that ADCs generated by BTG-ADC have improved pharmacokinetics and show a beter therapeutic index in in vivo models compared to brentuximab, with a significantly higher maximum tolerated dose (>60mg/kg vs 18 mg/kg) and a higher specific tumoral uptake.
Nicolaï Wagtmann, Chief Science Officer of Innate Pharma, noted: “We have developed a technology that allows obtaining rapidly homogenous ADCs based on a minimal change of the manufacturing process. This proprietary technology is highly versatile and can accommodate both existing and future high potency toxins. We have [also] demonstrated that BTG-ADCs are stable in vivo with a lower clearance compared to other available coupling technologies and have a more favorable biodistribution profile leading to an improved therapeutic index”.
A presentation of Innate Pharma’s BTG-ADC technology will be held at the upcoming European Antibody congress 2014, in Geneva, November 11, 2014 by Prof. Roger Schibli, PhD, ETH-Hönggerberg. Schibli is a scientific collaborator of Innate Pharma.