Astatine-211 is a promising radioisotope as a therapeutic tool due to the alpha particle emitted upon it radioactive decay. In order to use this property, it is necessary to bind it chemically to a carrier molecule able to transport it to the diseased cells to eradicate. Alpha particles being highly energetic but having a short penetration in tissues, their destructive action is limited to a small volume, therefore preventing damages to surrounding healthy tissues. However, the lack of knowledge on the basic chemistry on this element limits the available strategies to bind astatine efficiently to the carrier molecules of interest. The formation of a covalent astatine-carbon bond is frequently used, but this kind of bond is not robust enough to consider its use on human patient with sufficient safety. This project aims at carrying out an upstream research in order to assess the potential of alternative strategies to the astatine-carbon bond, which relies herein on the formation of astatine-metal bonds, and to determine if this approach has the potential for applications in nuclear medicine.

Tissue-resident lymphocytes represent promising effectors to treat pathologies in tissues. However, because these cells are largely located in tissues, they cannot easily be isolated in humans, and we lack the basic knowledge that would enable their generation in vitro for immunotherapeutic purposes. In this project, I propose to investigate in mice the basic mechanisms underlying the development and the transcriptional programming of tissue-residency features of a recently identified lineage of lymphocytes: the innate lymphoid cells (ILC). My postdoctoral work contributed to the identification and characterization of several developmental stages at which tissue-residency features are programmed in ILC. I now identified the developmental intermediates that initiate ILC development and tissue-residency programming. This breakthrough enables me to characterize the process of ILC development and tissue-residency programming in detail, and puts me in a unique position to decipher the mechanisms that underly these processes. This is what I propose to begin in this project, by investigating the function of two transcription factors that I find play key roles in respectively (i) initiating ILC development and tissue-residency programming, and (ii) enabling tissue-residency of ILC in specific tissues. The results will provide knowledge on the transcription factors that control ILC development and tissue residency programming. They enable subsequent work in which these factors could be manipulated to promote the generation of tissue-resident lymphocytes, or to modulate their functions. This basic research project will thus have broad implications for human health.

The mammary gland is a stratified epithelium made of ducts and lobulo-alveolar units that undergoes development and remodeling during the reproduction cycle. From pregnancy to lactation, steroid hormones induce proliferation and differentiation of luminal and basal cells for alveologenesis and lactation. At the end of lactation, the mammary gland regresses to go back to a quasi-virgin state, a process known as involution. It is associated with death of the majority of luminal alveolar cells, while basal cells resist to death and relocate to the ducts. Immune cells are recruited in close proximity to basal cells and clear the debris from dying luminal cells. The mechanisms that promote basal cell survival and immune cell recruitment and activation remain elusive. My preliminary data have revealed that a microtubule-based structure named the primary cilium is assembled in basal cells at involution and primary cilia promote survival of basal-like cells in vitro. Thus, we hypothesize that in the mammary gland, primary cilia promote basal cell survival which recruit and activate immune cells that clear luminal cell debris for proper tissue remodeling at involution. The PLIANCY project will directly address this hypothesis. In Aim 1, we will investigate the role of primary cilia in mammary gland involution through genetic and pharmacological perturbation of ciliogenesis at this stage, in mouse glands and organoids. In Aim 2, we will develop novel small-molecule inhibitors of ciliogenesis that will contribute to Aim 1 development and which will represent new important tools to better understand the biology of the cilium in physiology and physiopathology.

CAMERA proposal aims to give access to innovative radiopharmaceuticals labelled with 211 Astatine, an alpha-emitter very promising for use in nuclear medicine. At-labelled compounds are generally prepared using C-At covalent bonds that are not very stable which is detrimental for their use in biological applications. Other modality of bonding are needed to prepare more stable At-labelled compounds. For the first time, we wish to sequester Astatide anion (At-) using non-covalent interactions with high affinity in aqueous media. Cage-molecules displaying unprecedented affinities for Iodide, the halide with closest properties to At, will be choosen for the late-stage complexation of astatide. Cage-molecules will be functionalized with flexible arms able to interact with the encapsulated anions to further increase the stability of the formed complexes in aqueous media. Depending on the chemical functions that will be grafted on the periphery of the cage molecules, these new complexing agents may also be water-soluble and may have a fluorescent group to facilitate their monitoring. In order to maximize stability and selectivity, the synthesis work will be based on ab-initio calculations and extensive structural, thermodynamic and kinetic characterizations. This proposal will give new knowledge in supramolecular chemistry, in the chemistry of host-guest type cage molecules, in complexation of anions and more specially in Astate chemistry and applications. This work will open the way to the development of radiopharmaceuticals based on anion-chelation that are still unknown in contrast with bifunctional metal chelators used for radiometal complexation and bioconjugaison. This project will require effective collaboration between theoretical chemists for the design of cages, organic chemists for their synthesis and radiochemists for manipulations in the presence of radioactive anions and of biologists.

Targeted Alpha Therapy (TAT) is a new therapeutic modality in nuclear medicine based on the injection of alpha emitters coupled or not with biological vectors to treat patients with haematological or metastatic cancers. It is a very promising therapy whose rationale is based on the high cytotoxicity of alpha-particles and the limited irradiation of neighbouring tissues. This treatment modality is a major evolution in nuclear medicine. TAT indeed presents numerous new challenges to face in terms of production, radiochemistry, therapeutic indications, imaging, dosimetry and radiation protection. Three of the most promising alpha emitters, actinium-225, radium-223 and thorium-227, generate a decay chain producing alpha- and beta-emitters with short half-lives. This decay chain increases the tumouricidal potential of the treatment but it is also at the origin of the uncontrolled redistribution of radioactivity in the patient organs. With these "decay chain" alpha emitters, a mix of radionuclides will be present in the radiolabelling solution and inside the patient body. Toxicity has been observed in animal models due to this redistribution. It is essential, in the current of TAT development, to be able to follow, localise and quantify the micro-distribution of daughter radionuclides in tissues. This can only be done in preclinical experiments. The poor spatial resolution of imaging devices in clinics and the difficulty to acquire images from alpha emitters do not allow for sufficient high-resolution imaging on patients. The only imaging modality able to reach the required resolution is the autoradiography. However, current autoradiography devices do not allow for radionuclides discrimination on the images, in the presence of a mix of radionuclides. The autoradiography technology BeaQuant is developed by the AI4R company. It is based on a parallel ionisation multiplier gaseous detector. This new detector technology allows for the localisation of radioactive signals in real time. The BeaQuant characteristics make possible the development of Spectroscopic Alpha Autoradiography : i.e. a high-resolution (< 30 µm) imaging system able to display the radioactivity distribution in a solution or a tissue section and to discriminate 225Ac from its daughter radionuclides (221Fr, 217At and 213Bi). The "Laboratoire commun" AIDALab aims at proposing a new technological device and imaging, analysis and quantification process to help research labs and pharmaceuticals companies to address key challenges in the development of TAT. To that purpose, AIDALab will focus on three major research projects: i) technological innovation to develop Spectroscopic Autoradiographic Modalities (SAM) that are, in the end, able to produce imaging of each individual radionuclide present in a solution or a tissue ii) the development of a faster radiolabelling QC procedure using SAM iii) the development of new small-scale dosimetry methods to transform activity distribution images acquired with the BeaQuant into absorbed dose maps, essential to study treatment toxicity in normal tissues. AIDALab is composed by the AI4R company, based in Nantes, the develops new autoradiography devices and the "Nuclear Oncology" research lab (CRCI2NA) that has been focused on target radionuclide therapy and TAT for more than 20 years.