Catherine Paul

In vivo fluorescence lifetime imaging (FLI) is an advanced optical imaging modality with the capability to reveal additional biological information compared to fluorescence intensity (FI) imaging. In addition to enabling tissue discrimination based on microenvironmental variations, lifetime contrast allows the differentiation of spectrally overlapping fluorophores, thereby expanding the high potential of multiplexing imaging. Until now, most of the studies evaluating the benefits of in vivo FLI in terms of enhanced sensitivity and specificity for tumor imaging with fluorescent contrast agents have been conducted using heptamethine cyanine dyes. While these fluorophores are highly successful for conventional in vivo fluorescence imaging, they are characterized by short singlet excited-state lifetimes (generally below 1 ns), making it challenging to achieve satisfying tissue contrast and to implement multiplexing imaging strategies based on their lifetime differences. Here, we report a bioconjugatable, water-soluble NIR-emissive aza-BODIPY dye with a 100% longer lifetime than IRDye 800CW in physiological conditions. We demonstrate its suitability for in vivo FLI when conjugated to cetuximab and reveal how conjugation methods impact the lifetime characteristics of fluorescent antibody conjugates.

Protein bioconjugates are at the forefront of precision medicine, enabling the design of highly selective drugs for diagnostic and therapeutic applications. While increasing the number of payloads attached to a protein is a proven strategy to enhance the potency of a bioconjugate, the introduction of additional conjugation sites often risks compromising the protein’s targeting properties. In this study, we investigate the potential of 1,3,4-thiadiazole-N-oxides (TNO), a heterocyclic scaffold exhibiting excellent stability in biological media. We demonstrate that this reactive partner undergoes an unprecedented double addition reaction with bicyclo[6.1.0]non-4-yne derivatives. This unique reactivity is harnessed to achieve the site-specific attachment of two probes per conjugation site on a monoclonal antibody. Importantly, this strategy preserves antibody targeting properties, as confirmed by in vivo imaging studies. These findings establish TNO and the Strain-Promoted Alkyne-1,3,4-Thiadiazole-N-Oxide coupling (SPATOC) reaction as valuable new tools in the bioconjugation arsenal, expanding the possibilities for precise and efficient protein modification.

Background: The combination of antiangiogenic therapy with immune checkpoint blockade has demonstrated significant clinical benefits in various cancers, however, the precise mechanisms of action on the immune system are not fully understood. In particular, the early intratumoral immune responses induced by angiogenesis inhibition remain unclear. Methods: Using preclinical models of colorectal cancer, we examined the immune changes elicited by combined vascular endothelial growth factor receptor-2 (VEGFR-2) and programmed cell death protein-1 (PD-1) blockade. Results: Our findings reveal that CD8 T cells respond directly and early to VEGFR-2 inhibition, preceding the acquisition of overt cytotoxic function. Shortly after treatment, intratumoral CD8 T cells expanded and produced interleukin-10 (IL-10). Unexpectedly, this CD8 T cell-derived IL-10 promoted the recruitment of natural killer (NK) cells into tumors. Recruited NK cells subsequently gained effector activity and produced granulocyte-macrophage colony-stimulating factor, which supported macrophage maturation and the induction of CXCL11. This sequence of events enhanced secondary CD8 T-cell infiltration and sustained antitumor immune activity. Disruption of IL-10 signaling or NK-cell function eliminated the therapeutic benefit of combined VEGFR-2 and PD-1 blockade, whereas regulatory T-cell depletion further improved tumor control. Conclusions: Together, these findings identify an unanticipated role for CD8 T cell-derived IL-10 in coordinating early innate and adaptive immune responses following angiogenesis inhibition and define an immune program initiated by VEGFR-2 blockade that is required for therapeutic efficacy in two preclinical colorectal cancer models.

Real-time imaging of antibody-drug conjugates (ADCs) offers valuable insights for assessing tumor targeting specificity, monitoring therapeutic efficacy, and detecting off-target accumulation that may cause adverse effects. To enable precise tracking, we developed a versatile fluorescent platform based on an NIR-II emitting aza-BODIPY dye, which can be site-specifically grafted onto an IgG1 antibody to generate well-defined fluorescent ADCs. As a proof of concept, we synthesized an HER2-targeting trastuzumab immunoconjugate bearing a NIR-II aza-BODIPY fluorophore. The cytotoxic monomethyl auristatin E (MMAE) payload was introduced in the final step, resulting in a trackable and homogeneous ADC suitable for both in vitro and in vivo investigations. The resulting Trastu-azaNIRII-MMAE selectively accumulated in HER2-positive subcutaneous tumors, significantly reducing the tumor growth. Using NIR-II optical imaging, a single injection of the NIR-II-ADC allowed for the detection of the conjugate over a period of more than one month, highlighting its potential for long-term tracking and therapeutic applications.

The development of new fluorescent organic probes effective in the NIR-II region is currently a fast-growing field and represents a challenge in the domain of medical imaging. In this study, we have designed and synthesized an innovative series of aza-boron dipyrromethenes emitting in the NIR-II region. We have investigated the effect of different water-solubilizing groups not only on the photophysical properties of the compounds but also on their in vitro and in vivo performance after bioconjugation to the antibody trastuzumab. Remarkably, we discovered that the most lipophilic compound unexpectedly displayed the most favorable in vivo properties after bioconjugation. This underlines the profound influence that the fluorophore functionalization approach can have on the efficiency of the resulting imaging agent.

Detection of biomarkers to diagnose, treat, and predict the efficacy of cancer therapies is a major clinical challenge. Currently, biomarkers such as PD-L1 are commonly detected from biopsies, but this approach does not take into account the spatiotemporal heterogeneity of their expression in tumors. A solution consists in conjugating monoclonal antibodies (mAbs) targeting these biomarkers with multimodal imaging probes. In this study, a bimodal [¹¹¹In]-DOTA-aza-BODIPY probe emitting in the near-infrared (NIR) was grafted onto mAbs targeting murine or human PD-L1 either in a site-specific or random manner. In vitro, these bimodal mAbs showed a good stability and affinity for PD-L1. In vivo, they targeted specifically PD-L1 and were detected by both fluorescence and SPECT imaging. A significant benefit of site-specific conjugation on glycans was observed compared to random conjugation on lysine. The potential of this bimodal agent was also highlighted, thanks to a proof of concept of fluorescence-guided surgery in a human PD-L1+ tumor model.

(1) Background: Immunosuppression is a key barrier to effective anti-cancer therapies, particularly in triple-negative breast cancer (TNBC), an aggressive and difficult to treat form of breast cancer. We investigated here whether the combination of doxorubicin, a standard chemotherapy in TNBC with glyceryltrinitrate (GTN), a nitric oxide (NO) donor, could overcome chemotherapy resistance and highlight the mechanisms involved in a mouse model of TNBC. (2) Methods: Balb/C-bearing subcutaneous 4T1 (TNBC) tumors were treated with doxorubicin (8 mg/Kg) and GTN (5 mg/kg) and monitored for tumor growth and tumor-infiltrating immune cells. The effect of treatments on MDSCs reprogramming was investigated ex vivo and in vitro. (3) Results: GTN improved the anti-tumor efficacy of doxorubicin in TNBC tumors. This combination increases the intra-tumor recruitment and activation of CD8⁺ lymphocytes and dampens the immunosuppressive function of PMN-MDSCs PD-L1^low. Mechanistically, in PMN-MDSC, the doxorubicin/GTN combination reduced STAT5 phosphorylation, while GTN +/− doxorubicin induced a ROS-dependent cleavage of STAT5 associated with a decrease in FATP2. (4) Conclusion: We have identified a new combination enhancing the immune-mediated anticancer therapy in a TNBC mouse model through the reprograming of PMN-MDSCs towards a less immunosuppressive phenotype. These findings prompt the testing of GTN combined with chemotherapies as an adjuvant in TNBC patients experiencing treatment failure.

The human leucine-rich repeat-containing protein 15 (LRRC15) is a membrane protein identified as a marker of CAF (cancer-associated fibroblast) cells whose overexpression is positively correlated with cancer grade and outcome. Nuclear molecular imaging (i.e., SPECT and PET) to track LRRC15 expression could be very useful in guiding further therapeutic strategies. In this study, we developed an ScFv mouse phage-display library to obtain small fragment antibodies against human LRRC15 for molecular imaging purposes. Mice were immunized with recombinant human LRRC15 (hLRRC15), and lymph node cells were harvested for ScFv (single-chain variable fragment) phage-display analysis. The built library was used for panning on cell lines with constitutive or induced expression after transfection. The choice of best candidates was performed by screening various other cell lines, using flow cytometry. The selected candidates were reformatted into Cys-ScFv or Cys-diabody by addition of cysteine, and cloned in mammalian expression vectors to obtain batches of small fragments that were further used in site-specific radiolabeling tests. The obtained library was 1.2 × 10⁷ cfu/µg with an insertion rate >95%. The two panning rounds performed on cells permittedenrichment of 2 × 10⁻³. Screening with flow cytometry allowed us to identify 28 specific hLRRC15 candidates. Among these, two also recognized murine LRCC15 and were reformatted into Cys-ScFv and Cys-diabody. They were expressed transiently in a mammalian system to obtain 1.0 to 4.5 mg of Cys fragments ready for bioconjugation and radiolabeling. Thus, in this paper, we demonstrate the relevance of the phage-display ScFv library approach for the fast-track development of small antibodies for imaging and/or immunotherapy purposes.

The fluorescence of SWIR-WAZABI-01 is weak in aqueous solutions, while it is boosted in presence of LDL plasma lipoproteins which act as a carrier in vivo. Image created with BioRender.com.

Over the past decade, metabolic reprogramming has been defined as a hallmark of cancer. More recently, a large number of studies have demonstrated that metabolic reprogramming can modulate the differentiation and functions of immune cells, and thus modify the antitumor response. Increasing evidence suggests that modified energy metabolism could be responsible for the failure of antitumor immunity. Indeed, tumor-infiltrating immune cells play a key role in cancer, and metabolic switching in these cells has been shown to help determine their phenotype: tumor suppressive or immune suppressive. Recent studies in the field of immunometabolism focus on metabolic reprogramming in the tumor microenvironment (TME) by targeting innate and adaptive immune cells and their associated anti- or protumor phenotypes. In this review, we discuss the lipid metabolism of immune cells in the TME as well as the effects of lipids; finally, we expose the link between therapies and lipid metabolism.