Marie Le Cann

Françoise Bouhour

Karine Viala

Laurence Simon

Celine Tard

Cédric Rossi

Guillaume Morel

Emmeline Lagrange

Laurent Magy

Alain Créange

Céline Tard

Maud Michaud

Jérôme Franques

Andoni Echaniz-Laguna

Jean-Christophe Antoine

Marine Baron

Bertrand Arnulf

Angela Puma

Emilien Delmont

Thierry Maisonobe

Véronique Leblond

MD Damien Roos-Weil
email: damien.roosweil@aphp.fr

CANOMAD: a neurological monoclonal gammopathy of clinical significance that benefits from B-cell-targeted therapies

Keywords: CANOMAD, monoclonal gammopathy, MGCS, immunoglobulins, rituximab 2, Tables: 4 CANOMAD, chronic ataxic neuropathy, ophthalmoplegia, IgM paraprotein, cold agglutinins and disialosyl antibodies, CIDP, chronic inflammatory demyelinating polyneuropathy, FILO, French Innovative Leukemia Organization, IVIg, intravenous immunoglobulins, MGCS: monoclonal gammopathy of clinical significance, WM, Waldenström macroglobulinemia

Introduction

Monoclonal gammopathy of unknown significance (MGUS) is a common age-related condition, defined by the presence in serum and/or urine of a monoclonal immunoglobulin (Ig) produced by an abnormal B-cell clone, in the absence of overt plasma cell or B-cell lymphoproliferative diseases. Though mainly asymptomatic, these quiescent clones can be responsible for potentially severe organ damage, due to the toxicity of the monoclonal Ig or to other mechanisms, defining monoclonal gammopathy of clinical significance (MGCS) [START_REF] Fermand | Monoclonal gammopathy of clinical significance: a novel concept with therapeutic implications[END_REF] . This situation often requires therapeutic intervention, directed against the B-cell clone [START_REF] Merlini | Dangerous small B-cell clones[END_REF] . Along with the kidney and skin, the peripheral nerve is one of the most frequently involved organs.

Monoclonal gammopathies associated with peripheral neuropathy are more commonly IgM than IgG or IgA. The prevalence of neuropathy in patients with monoclonal IgM ranges from 5 to 31% [START_REF] Nobile-Orazio | Peripheral neuropathy in monoclonal gammopathy of undetermined significance: prevalence and immunopathogenetic studies[END_REF][START_REF] Steck | Anti-myelin-associated glycoprotein neuropathy[END_REF] .

Pathophysiologic mechanisms that link gammopathy and neuropathy include: i) specific autoantibody activity of the IgM against different components of the nerve, ii) specific properties of circulating IgM, leading to cryoglobulinemic neuropathy, amyloid or endoneurial IgM deposits, iii) nerve infiltration or nerve damage mediated by cytokine secretion of tumoral cells [START_REF] Fermand | Monoclonal gammopathy of clinical significance: a novel concept with therapeutic implications[END_REF][START_REF] D'sa | Investigation and management of IgM and Waldenstrom-associated peripheral neuropathies: recommendations from the IWWM-8 consensus panel[END_REF] . Autoreactive IgM most frequently recognize myelin-associated glycoprotein (MAG), but gangliosides can also be targeted. This latter activity can be responsible for a neurological syndrome termed CANOMAD (Chronic Ataxic Neuropathy, Ophthalmoplegia, IgM paraprotein, cold Agglutinins and Disialosyl antibodies), which is characterized by chronic neuropathy with sensory ataxia, and motor weakness involving oculomotor and bulbar muscles, occurring in the presence of monoclonal IgM directed against disialosyl ganglioside epitopes.

As some of the symptoms defining CANOMAD are not observed in all patients [START_REF] Willison | The clinical and laboratory features of chronic sensory ataxic neuropathy with anti-disialosyl IgM antibodies[END_REF][START_REF] Halpin | Buccoliero R A Case of CANOMAD with Review of the Literature[END_REF] , this acronym may be restrictive and the term CANDA (Chronic Ataxic Neuropathy with Disialosyl Antibodies) has also been proposed [START_REF] Yuki | Acute and chronic ataxic neuropathies with disialosyl antibodies: a continuous clinical spectrum and a common pathophysiological mechanism[END_REF] . The first case of neuropathy associated with monoclonal IgM with anti-ganglioside autoactivity was described in 1985 [START_REF] Ilyas | Monoclonal IgM in a patient with paraproteinemic polyneuropathy binds to gangliosides containing disialosyl groups[END_REF] and the largest series to date, published in 2001, comprised 18 patients [START_REF] Willison | The clinical and laboratory features of chronic sensory ataxic neuropathy with anti-disialosyl IgM antibodies[END_REF] .

Since then several case reports and small series have been reported in the literature, amounting to less than 50 cases [START_REF] Willison | The clinical and laboratory features of chronic sensory ataxic neuropathy with anti-disialosyl IgM antibodies[END_REF][START_REF] Ilyas | Monoclonal IgM in a patient with paraproteinemic polyneuropathy binds to gangliosides containing disialosyl groups[END_REF][START_REF] Arai | Ataxic polyneuropathy and anti-Pr2 IgM kappa M proteinemia[END_REF][START_REF] Willison | Peripheral neuropathy associated with monoclonal IgM anti-Pr2 cold agglutinins[END_REF][START_REF] Daune | Sensory neuropathy associated with monoclonal immunoglobulin M to GD1b ganglioside[END_REF][START_REF] Obi | IgM M-protein in a patient with sensory-dominant neuropathy binds preferentially to polysialogangliosides[END_REF][START_REF] Younes-Chennoufi | Ganglioside GD1b is the target antigen for a biclonal IgM in a case of sensory-motor axonal polyneuropathy: involvement of N-acetylneuraminic acid in the epitope[END_REF][START_REF] Yuki | Acute relapsing sensory neuropathy associated with IgM antibody against B-series gangliosides containing a GalNAc beta 1-4(Gal3-2 alpha NeuAc8-2 alpha NeuAc)beta 1 configuration[END_REF][START_REF] Herron | Monoclonal IgM cold agglutinins with anti-Pr1d specificity in a patient with peripheral neuropathy[END_REF][START_REF] Hitoshi | Cerebellar ataxia and polyneuropathy in a patient with IgM M-protein specific to the Gal(beta 1-3)GalNAc epitope[END_REF][START_REF] Willison | A somatically mutated human antiganglioside IgM antibody that induces experimental neuropathy in mice is encoded by the variable region heavy chain gene, V1-18[END_REF] . Symptoms are dominated by progressive chronic neuropathy with marked sensory ataxia that can lead to severe disability. In some cases, fluctuating or fixed symptoms such as ocular, sensory or bulbar manifestations are reported together with ataxia. The presence of antibodies directed against gangliosides is constant. The most frequently targeted gangliosides are GD1b, GD3, GT1b and GQ1b, which all harbor disialosyl groups containing the sequence NeuNAc (α2-8) NeuNAc (α2-3) Gal.

Such gangliosides are notably localized in the neurons of dorsal root ganglia and within the oculomotor nerves [START_REF] Kusunoki | Localization of GM1 and GD1b antigens in the human peripheral nervous system[END_REF] . In contrast to anti-MAG neuropathy, which is a predominantly distal demyelinating neuropathy, both axonal and demyelinating patterns have been reported using electrophysiological studies and nerve biopsies.

Investigation of IgM-associated peripheral neuropathy require a well-defined strategy that combine (1) nerve conduction studies (NCS) to distinguish between demyelinating and axonal patterns; (2) detection of anti-MAG and anti-ganglioside antibodies; (3) screening for "red flag" features (that include pain, multifocal topography, rapidly evolving course, cranial nerve involvement, dysautonomia, weight loss, cutaneous signs, heart/kidney/lung involvement, and abnormal serum-free light-chain concentration and ratio) to orientate further investigations and rule out in particular cryoglobulinemic/amyloid neuropathy and tumor nerve infiltration [START_REF] D'sa | Investigation and management of IgM and Waldenstrom-associated peripheral neuropathies: recommendations from the IWWM-8 consensus panel[END_REF][START_REF] Viala | Heterogeneous spectrum of neuropathies in Waldenstrom's macroglobulinemia: a diagnostic strategy to optimize their management[END_REF] .

There is actually no consensus for CANOMAD/CANDA treatment. Different therapeutic options have included intravenous immunoglobulins (IVIg), plasma exchange (PE), corticosteroids and immunosuppressive drugs [START_REF] Halpin | Buccoliero R A Case of CANOMAD with Review of the Literature[END_REF] . More recently, small case series have reported encouraging results with rituximab [START_REF] Delmont | Successful treatment with rituximab of one patient with CANOMAD neuropathy[END_REF][START_REF] Loscher | Successful treatment of CANOMAD with IVIg and rituximab[END_REF][START_REF] Garcia-Santibanez | CANOMAD and other chronic ataxic neuropathies with disialosyl antibodies (CANDA)[END_REF][START_REF] Siddiqui | Chronic ataxic neuropathy with cold agglutinins: atypical phenotype and response to anti-CD20 antibodies[END_REF] . Finally, although virtually all cases of CANOMAD/CANDA syndrome are associated with the presence of a monoclonal IgM, the spectrum of underlying hematologic malignancies and the efficacy of B-cell-targeting therapies have not been thoroughly investigated.

Main objectives of this retrospective study were to describe the clinical features of CANOMAD/CANDA syndrome, to identify associated hematologic malignancies and to gain insights into its optimal therapeutic management, while studying the largest patient cohort to date.

Patients, material and methods

Patients

This study is a national retrospective analysis of 45 patients, treated in 17 centers, which were included in a CANOMAD multicenter French registry between 2002 and 2018 on the basis of the positivity of at least one serum IgM antibody reacting against disialosyl epitopes (among GD1b, GD3, GT1b and GQ1b) and evocating neurological signs. A standardized questionnaire on demographics, clinical, biological, electrophysiological and therapeutic data was sent to all referring clinicians.

IVIg treatment consisted of a dose of 2 g/kg every 4 weeks. This interval between courses could be gradually increased by one week in case of clinical improvement. IVIg treatment could be stopped in case of clinical complete response. Administration schedules of single-agent rituximab were weekly infusions of 375 mg/m 2 for four weeks (n = 13) or two infusions of one g/m 2 on days 1 and 15 (n = 6).

Clinical data were obtained in accordance with the Declaration of Helsinki and its later amendments. All patients were informed and consented to participate in this study prior to inclusion in the registry.

Three cases have been published previously as case reports [START_REF] Delmont | Successful treatment with rituximab of one patient with CANOMAD neuropathy[END_REF][START_REF] Delval | Relapsing sensorimotor neuropathy with ophthalmoplegia, antidisialosyl antibodies, and extramembranous glomerulonephritis[END_REF][START_REF] Attarian | Chronic ataxic neuropathies associated with anti-GD1b IgM antibodies: response to IVIg therapy[END_REF] .

Investigations

Detection of monoclonal gammopathies, cold agglutinins and anti-ganglioside antibodies were performed locally and were part of variables collected in the standardized questionnaire. Methods testing for the presence of anti-disialosyl antibodies comprised enzyme-linked immunosorbent assay (ELISA) [START_REF] Willison | The clinical and laboratory features of chronic sensory ataxic neuropathy with anti-disialosyl IgM antibodies[END_REF][START_REF] Willison | Inter-laboratory validation of an ELISA for the determination of serum anti-ganglioside antibodies[END_REF] , "home-made" immunodots [START_REF] Caudie | Comparison of commercial tests for detecting multiple anti-ganglioside autoantibodies in patients with well-characterized immune-mediated peripheral neuropathies[END_REF] or commercial tests (Generic Assays, Courtaboeuf, France).

The Generic Assays commercial test (AntiGangliosidDot) is a line immunoassay used for the qualitative detection of IgM antibodies directed against 11 gangliosides (GM1, GM2, GM3, GM4, GD1a, GD1b, GD2, GD3, GT1a, GT1b, GQ1b) while "home-made" assay detect antibodies directed against 8 gangliosides (GM1, GM2, GM3, GD1a, GD1b, GD2, GT1b, GQ1b). Routine screening investigations to exclude other causes of neuropathy followed recommendations previously published 5 and were negative. Electrophysiological studies were carried out locally in all cases and centrally reviewed. Axonal and/or demyelinating damages were defined according to the Ad Hoc Subcommittee of the American Academy of Neurology AIDS task Force's demyelination criteria [START_REF]Research criteria for diagnosis of chronic inflammatory demyelinating polyneuropathy (CIDP). Report from an Ad Hoc Subcommittee of the American Academy of Neurology AIDS Task Force[END_REF] . Bone marrow examination was performed in 31/45 (69%) patients.

Definitions

CANOMAD and CANDA were defined as described in the Introduction section and in previous publications [START_REF] Willison | The clinical and laboratory features of chronic sensory ataxic neuropathy with anti-disialosyl IgM antibodies[END_REF][START_REF] Yuki | Acute and chronic ataxic neuropathies with disialosyl antibodies: a continuous clinical spectrum and a common pathophysiological mechanism[END_REF] . Diagnoses of associated hematologic malignancies followed the WHO classification criteria [START_REF] Swerdlow | The 2016 revision of the World Health Organization classification of lymphoid neoplasms[END_REF] .

To assess treatment response, we used the modified Rankin score (RS) (a 7-point disability rating scale with scores from zero (no deficit) to six (death)) evaluating the degree of disability or dependence for daily activities [START_REF] Wilson | Improving the assessment of outcomes in stroke: use of a structured interview to assign grades on the modified Rankin Scale[END_REF] . Clinical response was defined as complete response (CR, complete clinical improvement from baseline, RS=0), partial response (PR, a clinical improvement defined as ≥ 1-point RS decrease), stable disease (SD, unchanged RS) and progression (≥ 1-point RS increase). The different lines of therapy were separately analyzed for each patient. Biological response was defined as CR (disappearance of IgM and negative immunofixation), PR (decrease in serum IgM levels > 50%), SD (increase < 25% or decrease < 25%) and progression (increase > 25%).

Statistics

Overall survival was calculated from date of diagnosis until last follow-up/death and time to next treatment from date of first-to second-line of treatment. Kaplan-Meier analysis was performed to construct survival curves and the log rank test used to determine differences between groups. The Χ 2 or Fisher's exact test were used to compare data distribution in different clinical or treatment subgroups.

The significance level of p < 0.05 was applied and statistical analyses were performed using the SPSS software.

Data Sharing Statement

For original data, please contact damien.roosweil@aphp.fr.

Results

Clinical features

Main clinical characteristics are provided in Table 1. Of the 45 patients included in our study, 35 (78%) were male. Median age at onset of symptoms was 58 years (range, 37-81) and the median delay between onset of symptoms and diagnosis of CANOMAD/CANDA was 4.0 years (range, 0.1-27). The most frequent initial symptoms were sensory (paresthesia and ataxia in respectively 26 (58%) and 21 (47%) cases), ocular (n=6, 13%) and bulbar (n=3, 7%). Of note, the disease was revealed by isolated ophthalmoplegia in one patient. At CANOMAD/CANDA diagnosis, nearly half (n=19, 44%) of the cohort harbored significant disability (modified Rankin score of 3 to 5). Clinical outcome was mainly chronic progressive (n=30, 67%) or relapsing-remitting (n=14, 31%). One patient experienced one symptomatic flare-up that completely resolved after first-line therapy. The set of neurological symptoms observed during the course of the disease for the whole cohort are detailed in Table 1.

Serological analyses and others investigations

All patients had anti-ganglioside antibodies with IgM specificity, reacting against at least one out of four of the following disialosyl epitopes: GD1b, GD3, GT1b and GQ1b. Thirty (67%) and 21 (47%) patients had antibodies reacting against at least 3 or 4 out of 4 of the mentioned epitopes. Forty (89%) had also antibodies reacting against other gangliosides such as GM1, GM2, GM3, GD1a, GD2 or GT1a.

Regarding cerebrospinal fluid (CSF) analysis, the mean protein level was 0.9 g/L (range, 0-2) and cellularity was negative in 80% of cases (median, 0/mm 3 ; range, 0-4). Nerve conduction studies (NCS) showed a demyelinating or axonal pattern in respectively 27 (60%) and 12 patients (27%). Among the six patients for whom electrophysiological studies were normal, two had abnormal somatosensory evoked potential, corresponding to a particular form of peripheral neuropathy, characterized by demyelination involving the proximal part of the sensory nerves [START_REF] Sinnreich | Chronic immune sensory polyradiculopathy: a possibly treatable sensory ataxia[END_REF] ; it could be undetectable by classical NCS. One patient had a form of small fiber neuropathy, which is also usually not detected by classical NCS. Two other patients had only very mild sensitive symptoms when NCS were performed. Fourteen nerve biopsies were performed revealing demyelinating, axonal and mixed features in respectively four, five and four cases. One patient had a normal nerve biopsy. Three cases presented additional abnormalities: endoneural fibrosis (n=1), IgM deposits identified by immunofluorescence (n=1), and epineural lymphocyte infiltrate without precision (n=1).

Associated hematologic and non-hematologic malignancies

All patients (n=45) harbored a monoclonal IgM gammopathy detected by immunofixation. The monoclonal light chain was kappa in 19/45 (42%) and lambda in 21/45 (49%) patients. Five patients had both monotypic kappa and lambda IgM. The median peak value was 2.6 g/L (range, 0.1-40). Cold agglutinins were identified in 15 out of the 44-screened cases (34%) but their specificity was not available in most cases. None had active hemolysis.

Overt associated hematologic malignancies were identified in 16 patients (36%). These diagnoses were made before, after or were concomitant to those of CANOMAD/CANDA in respectively four (25%), four (25%), and eight (50%) patients. One patient required treatment for B-cell malignancy before CANOMAD/CANDA diagnosis. The most frequent associated hematologic malignancy was Waldenström macroglobulinemia (WM) (n=9, 20%). Other documented hematologic neoplasms included diffuse large B-cell lymphoma (n=2, 4%, including one transformation of WM), monoclonal B lymphocytosis (n=2, 4%), chronic lymphocytic leukemia (n=1, 2%), marginal zone lymphoma (MZL) (n=1, 2%), unclassifiable small B-cell lymphoma (n=1, 2%) and mantle cell lymphoma (n=1, 2%) (Table 2). Clinical characteristics of CANOMAD/CANDA were largely similar between patients with or without an overt associated hematologic malignancy, notably in terms of ocular or bulbar involvement and degree of disability, and were no significantly associated with the level of IgM peak value (Supplemental

Table S1, S1bis and S1 ter).

Three patients developed solid tumors during their follow-up, i.e. bronchopulmonary cancer (n=2) and glioblastoma (n=1). These diagnoses were concomitant in one case and largely posterior to those of CANOMAD/CANDA in two cases (6 and 18 years).

Treatment and outcomes

Forty-one (91%) patients received treatment for CANOMAD/CANDA, including two patients treated by CHOP regimen for concomitant symptomatic hematologic malignancy. Among the four patients that did not receive treatment, three had minor symptoms (modified Rankin score of 1) and a very indolent course with a follow-up of more than 5 years each. One patient had a very aggressive and disabling CANOMAD syndrome revealed by acute respiratory distress secondary to phrenic paralysis and died within a few weeks due to pulmonary complications.

The median number of therapeutic lines was two (mean, 3.0; range, 1-7), corresponding to a cumulative number of 135 lines of treatment for the whole cohort. The median delay between CANOMAD/CANDA diagnosis and initiation of treatment was 4 months (range, 0-168). First-line treatment consisted in IVIg (n=20/41, 49%), corticosteroids (n=11/41, 27%), plasma exchange (PE) (n=3/41, 7%), chlorambucil (n=3/41, 7%), CHOP regimen (n=2/41, 5%), azathioprine (n=1/41, 2%) or rituximab (n=1/41, 2%) (Table 3). Of note, clinical characteristics, especially regarding the degree of disability before treatment, were similar between the two largest groups of first-line treatment (IVIg and corticosteroids) (data not shown).

Overall clinical response was obtained in 18 (44%) patients, including four (10%) CR and 14 (34%) PR, while stable disease and progression were respectively observed in seven (17%) and 16 (39%) cases (Table 3 and Supplemental Figure S1). Type of first-line treatment impacted quality of response as overall clinical responses were obtained in 60% of patients treated by IVIg and in only one patient (10%) with corticosteroids, correlating with a respective median decrease of 1 point (range, +1 to -4) and increase of 1 point (range, 0 to +2) in modified Rankin score.

Thirteen patients (32%) received only one line of treatment, which consisted in IVIg (n=9), single agent rituximab (n=1), plasma exchange (n=1) and CHOP regimen (n=1). Median time to next treatment was respectively 23 (range, 1-101) and 35 months (range, 4-101) for the whole cohort and first-line IVIg (Supplemental Figure S3B andC).

Different types of therapies used in first and subsequent lines of treatment (n=135) are summarized in Table 4. The most frequently used treatments were IVIg (n=55/135, 41%), rituximab-based regimens (n=19, 14%), corticosteroids (n=14, 10%), immunosuppressive therapies (n=14, 10%), plasma exchange (n=8, 6%), chlorambucil (n=6, 4%), and other chemotherapy regimens (n=5, 4%). While IVIg and rituximab-based regimens were associated with overall clinical responses of respectively 53 and 52%, corticosteroids and immunosuppressive therapies were largely ineffective with respectively 14 and 0% of overall clinical responses (Table 4 and Supplemental Figure S2).

With a median follow-up time from the onset of neurological symptoms of 127 months (range, 1-434) for the whole cohort, 30 (65%) patients were still alive at their last follow-up. The median OS of our cohort was not reached (range, 0.16-31 years) (Supplemental Figure S3A). Deaths were related to CANOMAD/CANDA, hematologic malignancies or other causes in respectively five (33%), three (20%) and seven (47%) cases. Others causes included progressive solid tumors (n=3, comprising the aforementioned bronchopulmonary cancer [n=2] and glioblastoma [n=1]), infectious (n=2) and cardiovascular (n=2) complications.

Rituximab-based regimens

Nineteen patients were treated with a regimen including rituximab, in first-line (n=1) or subsequent lines of treatment (n=18). Five patients received a rituximab-based regimen twice or more. The median line of treatment of rituximab-based regimens was three (range, 1-7). Tolerance of rituximab was excellent with the exception of one anaphylactic shock that resolved after corticosteroid therapy. No IgM flare was reported.

Rituximab-based regimens consisted in rituximab monotherapy (n=13), immunochemotherapy (ICT) combination (n=4) (rituximab-fludarabine, n=2; rituximab-cyclophosphamide-dexamethasone, n=2) or other regimens (rituximab-ibrutinib, n=1; rituximab-corticosteroids, n=1). ICT was used in patients with an overt hematologic malignancy (WM, n=3; MZL, n=1). Five patients were retreated with a second course of single-agent rituximab upon disease progression. This rechallenge led to similar or improved clinical responses. Biological responses to rituximab-based regimens were available or interpretable (pre-treatment IgM peak value above 0.5 g/L) in 14/19 cases, correlated well to clinical responses and were distributed as follows: two CR (corresponding to one clinical CR and one clinical PR), six PR (corresponding to five clinical PR and one clinical PR), five SD (corresponding to four clinical SD and one clinical progression) and one progression (corresponding to one clinical progression) (Figure 1 and Supplemental Table S2). Considering first-use of rituximab-based regimens (n=14), median time to next treatment was 45 months (range, 2-100) (Supplemental Figure S3D).

Five additional patients received both single agent rituximab and IVIg that precluded single evaluation of each drug efficacy (Table 3).

Discussion

To our knowledge, this is the largest retrospective series of CANOMAD/CANDA available to date. In this series, we confirmed many of the already published clinical features, extended our knowledge of different clinical presentations, characterized the spectrum of associated hematologic malignancies and highlighted IVIg and rituximab-based regimens efficacy.

Consistent with previous studies, most patients were male, in the fifth decade of life and were disabled by sensory ataxia. However, even if sensory symptoms were predominant, they were not specific and clinical presentation in our series was less homogeneous than previously described [START_REF] Willison | The clinical and laboratory features of chronic sensory ataxic neuropathy with anti-disialosyl IgM antibodies[END_REF] . Only 19/45 (42%) patients recapitulated all the features of CANOMAD. Ophthalmoplegia was only observed in 44% and severe forms (modified Rankin score of 4-5) were not rare (27%). Also, in keeping with others studies, all patients had anti-ganglioside antibodies with IgM specificity, reacting against GD1b, GD3, GT1b or GQ1b, and around half of the cohort had antibodies directed against these four disialosyl epitopes, emphasizing that they are key biological elements for diagnosis. All the data mentioned above plead for a more extensive entity that the acronym CANDA (chronic ataxic neuropathy with disialosyl antibodies) could better encompass, as previously suggested [START_REF] Yuki | Acute and chronic ataxic neuropathies with disialosyl antibodies: a continuous clinical spectrum and a common pathophysiological mechanism[END_REF] . From a practical point of view, CANOMAD/CANDA must be suspected in case of sensory symptoms associated with ocular or bulbar motor disorders but also in case of isolated sensory forms especially if: i) there is ataxia (present in half of cases), ii) the disease progresses in flare-ups, and/or iii) anti-MAG antibodies are negative. This also emphasizes the need for cooperation between hematologist and neurologist in difficult cases.

This study is the first to describe comprehensively the spectrum of hematologic malignancies associated with CANOMAD/CANDA. All patients had detectable serum monoclonal IgM. Although no monotypic light chain predominance was observed, there is a possible bias toward lambda expression (49%) in our cohort in comparison to the 70-80% of monotypic kappa expression usually reported in IgM MGUS [START_REF] Morra | Clinical characteristics and factors predicting evolution of asymptomatic IgM monoclonal gammopathies and IgM-related disorders[END_REF] .

As anticipated by the presence of monoclonal IgM, the identified associated hematologic malignancies were B-cell lymphoproliferative disorders, which accounted for around one third of the cohort and mainly consisted of WM (56%). Of note, only 31 (69%) patients of our cohort had bone marrow examination, possibly underestimating the proportion of patients with overt associated hematologic malignancy.

Clinical features of CANOMAD/CANDA can precede, be concurrent to or appear during follow-up of a previously treated hematologic malignancy. The clinical course was highly variable with some patients being wheelchair users after few months despite therapeutic intervention and others remaining mobile after more than 10 years of follow-up without any treatment. Treatments used in our CANOMAD/CANDA series were very heterogeneous (> 10) but most of them corresponded to those used in chronic inflammatory demyelinating polyneuropathy (CIDP). Indeed, as for CIDP, IVIg and corticosteroids (31/41, 75%) represented the most frequent first-line treatments. Global overall clinical responses to first-line treatment in our cohort was 44% and was mostly seen in patients treated with IVIg (60%).

Efficacy rate of IVIg was in accordance with those reported in previous studies in CIDP (40-60%) [START_REF] Latov | Diagnosis and treatment of chronic acquired demyelinating polyneuropathies[END_REF] and CANOMAD/CANDA (55-68%) [START_REF] Halpin | Buccoliero R A Case of CANOMAD with Review of the Literature[END_REF][START_REF] Garcia-Santibanez | CANOMAD and other chronic ataxic neuropathies with disialosyl antibodies (CANDA)[END_REF] . Of note, the efficacy of IVIg was similar whether used as first-line treatment or in the relapse/refractory setting, with overall clinical responses obtained in around half of the cases. In contrast to its observed efficacy in CIDP (40-60%) [START_REF] Latov | Diagnosis and treatment of chronic acquired demyelinating polyneuropathies[END_REF] and previous experiences in CANOMAD/CANDA (30-50%) [START_REF] Halpin | Buccoliero R A Case of CANOMAD with Review of the Literature[END_REF][START_REF] Garcia-Santibanez | CANOMAD and other chronic ataxic neuropathies with disialosyl antibodies (CANDA)[END_REF] , corticosteroids were very rarely effective (13%) in our series.

Although less frequently used, plasma exchange efficacy was also similar to previous reports with clinical responses observed in 40-50% of cases.

Considering the constant presence of a monoclonal IgM that produces the anti-ganglioside antibody activity and recapitulates clinical features, CANOMAD/CANDA should be considered as a neurological subtype of MGCS [START_REF] Fermand | Monoclonal gammopathy of clinical significance: a novel concept with therapeutic implications[END_REF] . In this regard, our data highlighted the benefit of targeting the B-cell clone in CANOMAD/CANDA as it is already done in other types of MGCS. Rituximab-based regimens showed an efficacy rate of 53%, similar to the one observed with IVIg. They were mostly used in second or subsequent lines of treatment in patients that already experimented IVIg. Efficacy of rituximab-based regimens was comparable in patients with or without an associated hematologic malignancy. These results are in line with the efficacy reported with rituximab in anti-MAG neuropathy [START_REF] Dalakas | Placebo-controlled trial of rituximab in IgM anti-myelin-associated glycoprotein antibody demyelinating neuropathy[END_REF][START_REF] Leger | Placebo-controlled trial of rituximab in IgM antimyelin-associated glycoprotein neuropathy[END_REF] and in non-CANOMAD/CANDA CIDP associated with hematologic malignancies [START_REF] Roux | Rituximab in chronic inflammatory demyelinating polyradiculoneuropathy with associated diseases[END_REF] .

This study has limitations due in part to its retrospective design encompassing a long period of time.

Data is lacking regarding delay of response to treatment, preventing us from drawing conclusions as to which treatment could be better suited to patients with rapidly progressive disease. Additionally, clinical evaluation was not centrally reviewed, although all patients were followed up in CANOMAD neurological reference centers.

Several questions remain unanswered about the management of CANOMAD/CANDA patients. Further studies will determine if rituximab can allow safe withdrawal of IVIg in responding but dependent patients. For patients whose response to rituximab is insufficient, immunochemotherapy with adjunction of alkylating agents may improve outcomes obtained with single agent rituximab, as it has been reported for anti-MAG neuropathy [START_REF] Hospital | Immunotherapy-based regimen in anti-MAG neuropathy: results in 45 patients[END_REF] . Alternatively, more recently developed targeted B-cell drugs such as BTK and BCL2 inhibitors, that have demonstrated clinical efficacy in treatment of WM and other B-cell lymphoproliferative disorders [START_REF] Castillo | What is new in the treatment of Waldenstrom macroglobulinemia?[END_REF][START_REF] Furstenau | Sequential and combination treatments with novel agents in chronic lymphocytic leukemia[END_REF] , could be of potential benefit. Based on our cohort and systematic analysis of the literature, we propose a therapeutic algorithm for CANOMAD/CANDA management (Figure 2). First-line IVIg treatment appears to be the most efficient and validated therapeutic option. IVIg refractory or relapsed forms require rituximab-based regimens as single-agent or in association with alkylating agents. IVIg rechallenge could be proposed in case of longlasting remission after first-line IVIg treatment.

In conclusion, CANOMAD/CANDA is a rare, frequently debilitating and probably underdiagnosed syndrome, which is associated with an overt hematologic malignancy, mainly WM, in one third of patients. IVIg and rituximab-based regimens are the most effective therapies. Corticosteroids and immunosuppressive drugs should not be used. Similar to anti-MAG neuropathy, CANOMAD/CANDA should be considered as neurological subtype of MGCS and therefore could benefit from B-cell directed therapies. More studies are warranted to better characterize the correlation between clinical and biological responses and define the optimal therapeutic options and sequence.

Tables

Acknowledgements:

  This study was supported (in part) by INCA-DGOS-Inserm_12560 : SiRIC CURAMUS is financially supported by the French National Cancer Institute, the French Ministry of Solidarity and Health and Inserm with financial support from ITMO Cancer AVIESAN (Alliance Nationale pour les Sciences de la Vie et de la Santé/ National Alliance for Life Sciences & Health). Contribution statement: MLC, FB, KV, LS, VL and DRW designed the research, analyzed data and wrote the manuscript. MLC, FB, KV, LS, CT, CR, GM, EL, LM, ED, MM, JF, AEL, JCA, MB, BA, ARP, AC, TM, VL and DRW recruited patients. FB centrally reviewed all electrophysiological data. All authors reviewed and approved the manuscript. Conflict-of-interest disclosure: VL reports receiving honoraria and advisory board fees from Roche.

Figure 2

 2 Figure 2

Table 1 .

 1 Main clinical and electrophysiological characteristics of CANOMAD/CANDA patients. Therapeutic algorithm for CANOMAD/CANDA management. CR, complete response; IVIg, intravenous immunoglobulin; PE, plasma exchange; PR, partial response; SD, stable disease.

	Characteristics	No. (%)
	Total	45 (100)
	Male	35 (78)
	Age at CANOMAD/CANDA diagnosis, years
	Median (range)	62 (38-81)
	Time from onset of symptoms to CANOMAD/CANDA
	diagnosis, years
	Median (range)	4 (0.1-27)
	Type of onset
	Acute	8 (18)
	Subacute (rapidly progressive)	7 (15)
	Chronic (slowly progressive)	30 (67)
	Neurological symptoms at diagnosis
	Sensory symptoms	35 (78)
	Paresthesia	26 (58)
	Ataxia	21 (47)
	Ophthalmoplegia	6 (13)
	Bulbar symptoms	3 (7)
	Others	14 (31)
	Painful limb	6 (13)
	Motor weakness/myoclonus	3 (7)
	Acrocyanosis/livedo	2 (4)
	Dyspnea	1 (2)
	Facial nerve paralysis	1 (2)
	Neurological symptoms during the course of the disease
	Sensory ataxia	34 (76)
	Paresthesia	35 (78)
	Hypoesthesia	42 (93)
	Upper and lower limbs	24 (53)
	Lower limbs only	18 (40)
	Ophthalmoplegia	20 (44)
	Bulbar symptoms	6 (13)

Early relapse: relapse during IVIg tapering or < 2 years after IVIg treatment Late relapse: > 2 years after IVIg treatment Early relapse: relapse during IVIg tapering or < 2 years after IVIg treatment Late relapse: > 2 years after IVIg treatment

Motor weakness 18 (40) Upper and lower limbs 13 (29) Lower limbs only 5 (11) Areflexia 42 (93)

Facial nerve paralysis 3 (7) Dysautonomic signs 2 (4)

Acute respiratory distress 3 (7) Modified Rankin score at diagnosis /42 0 (asymptomatic) 0 (0)

Abbreviations: CR, complete response; PR, partial response; SD, stable disease S2).


Marie-France Robbe

Michel Lepareux

Yves Cariou

Interpretation with the Europlexus code of the MARA8 experiment simulating a hypothetical Core Disruptive Accident

des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.


Dr Thomas Delouche

Dr Thierry Roisnel

Dr Vincent Dorcet

Muriel Hissler
email: muriel.hissler@univ-rennes1.fr

Pierre-Antoine Bouit
email: pierre-antoine.bouit@univ-rennes1.fr

Prof M Hissler

Dr P-A Bouit

Mixing Polyaromatic Scaffolds and Main Group Elements: Synthesis, Coordination and Optical Properties of Naphthyl-Fused Heteropines

Polyaromatic 7-membered rings featuring main group elements (P, Ge) are described. Coordination complexes were synthesized with the trivalent phosphepines highlighting that these P-heterocycles are promising ligands. Furthermore, those polyaromatic germepines and phosphepines appear as interesting building blocks for optoelectronics.

INTRODUCTION

Polycyclic Aromatic Hydrocarbons (PAHs) have been attracting attention since decades but the discovery of graphene prompted the scientific community to intensify the study of graphene molecular analogs (also called nanographenes). These organic compounds are composed of sp 2 -C atoms and can be planar or distorted. Their particular structure confers them unique properties in term of reactivity, optical/redox activity, self-assembly and opto-electronic device performances. [1] They are thus an important class of organic semi-conductors. A strategy to modify the properties of PAHs is to switch from benzenoids structures to compounds featuring various ring sizes [2] or to introduce heteroatoms (O, S, N, B, P, Si ...). [3] Both strategies can also be combined. In this context, the synthesis of heteropines (7-membered heterocycles featuring heteroelement) recently appeared as an appealing strategy. [4] For example various naphthylfused heteropine incorporating oxygen A [5], boron B [6], nitrogen C [7] or phosphorus D [8] have been described in the last years (Scheme 1). All these -extended heteropines display a strongly distorted C-framework and can be emissive in solution. The insertion of the heteroatom allows modifying the molecular distortion and tuning the optical properties. In the present article, we detail the molecular engineering and the reactivity of our recently reported naphthyl-fused phosphepine. [8] As an extension of the synthetic strategy, the synthesis of germanium-containing heteropine (germepine) was investigated (Scheme 1). Furthermore, we report on a detailed study on the optical properties of the phosphepine and germepine.

Distorted -systems featuring main group elements Scheme 1. Naphtyl-fused heteropines described in the literature: Oxepine (A), Borepine (B), Azepine (C), Phosphepine (D) and synthetic strategy developed in this article.

RESULTS AND DISCUSSION.

The phosphepine 3 can be synthesized through a Yamamoto coupling involving Ni-coupling on the dibromonaphtylphenylphosphine oxyde 1 (Scheme 2). [8], [START_REF] Zhang | Alternative route toward naphthyl-fused phosphepine and phosphepine oxide: (a)[END_REF] Since this reaction is very air and moisture sensitive, we tested an Ullmann coupling, another well-known strategy to realize C-C coupling. [10] The advantage of this pathway is the use of Cu(0) which is less air and moisture sensitive than Ni(0). This approach was tested on 1 in classical Ullman conditions (Cu(0), DMF). This methodology surprisingly led to the formation of the phosphocine 2 (Scheme 2), an 8membered ring including a phosphorus and an oxygen atom. [START_REF] Wang | For example of Cu-catalyzed O-arylation[END_REF] The most favorable explanation of this compound formation would be the presence of water traces in the media. Indeed, adding water in the media, allowed increasing the yield until 35%. Interestingly, the Ullmann coupling leads to the 8-membered ring (2) only with the precursor with the exocyclic P-Ph bond (1). When the P-atom is substituted with alkoxy or aryloxy (4, 5, Scheme 2), the Ullmann coupling leads to the formation of seven-membered rings: phosphepine 6 and 7 (Scheme 2). However the yields are smaller compared to the Yamamoto coupling involving Ni-coupling (Scheme 2). All compounds were fully characterized by means of multinuclear NMR spectroscopy and mass spectrometry. Scheme 2. Ullmann and Yamamoto coupling on the precursor 1, 4-5 leading to the phosphocine 2 and the phosphepines 3, 6-7

Phosphocine 2 was characterized by X-ray diffraction (Figure 1 and Table S1-S2). The X-ray structure shows that the 8membered ring 2 adopts a bended structure with an angle between the naphthyl groups of 121.87° and non-bonding peri-distance d(O•••P) = 2.79 Å, in the range of previously reported P,O peri-substituted naphthalenes. [12] It is worth mentioning that the two naphthyl groups keep their planarity. On the contrary, the 7-membered ring 3 adopts a twisted structure with a torsion angle between the naphthyl groups of 35.80°. [8] As for the phosphepine, the P-C bonds lengths are classical for phosphine-like structures (dP-C = 1.79-1.80 Å). In the 8-membered P-ring, all C-C bonds belonging to the naphthalene moiety are within the aromatic C-C distances (1.41 Å< d< 1.44 Å). The C-O bonds also display classical distances (1.39 Å< d< 1.40 Å). With the naphthyl-fused phosphepine oxide 3 in hands, we were interested in testing whether this P-atom locked in a distorted P-heterocycle remains reactive. Thus, the phosphorus atom of compound 3 was deprotected by a reductive treatment with HSiCl3 allowing to obtain the  3 , 3 -phosphepine 8. Then, this intermediate was directly reacted with MeOTf to afford cationic derivative 9 or with various metallic ions to afford quantitatively coordination complexes 10 with Au(I), 11 with Re(I) and 12 with Pd(II)(Scheme 3). All compounds were fully characterized by means of multinuclear NMR spectroscopy and mass spectrometry and complexes 10 and 12 were additionally characterized by X-ray diffraction (vide infra). This study shows that naphthyl-fused phosphepines display the classical reactivity of  3 , 3 -phosphane which allows to easily diversify its molecular structures. Scheme 3. Synthesis of the naphthyl-fused phosphepinium 9 and the phosphepine complexes 10-12.

Complexes 10 and 12 were characterized by single-crystal X-ray diffraction. In the X-ray structure of 10 and 12, metric parameters of the polycyclic framework of the phosphepine ligand are similar to those of the previously reported phosphepine 3 (Table S3). [8] Complex 10 crystallizes in the P-1 space group of the triclinic system (Table S1). In this derivative, the P-center of the ligand L acts as expected, as a two-electron donor toward the Au(I) metal center (d(P-Au), 2.246 Å) and the P-Au-Cl fragment is almost linear (P-Au-Cl, 177.1°). Complex 12 crystallizes in the P 21/n space group of the triclinic system (Table S1). The P-Pd bond lengths are classical for a phosphine  3 -P center acting as two electron donor on a Pd(II) metal center (d(P-Pd), 2.327) Å.Furthermore, a distorted square planar geometry is observed around the Pd(II) ion (87.8° < P-Pd-Cl < 92.2°) with the two P-ligands coordinated on trans-position and the P-Ph in trans of the P-Pd-P fragment (Fig. 2). This situation markedly differs compared to our previously reported Pd-complex featuring two planar P-containing PAH ligands in which intra-complex -stacking induced an unconventional cisconformation. [13] The present behavior can be attributed to the distorted -surface of the ligand 8 which prevent interligands interactions. Furthermore, the distorted phosphepine backbone also prevents inter-complexes interactions. Based on those examples, the rich coordination chemistry of phosphine can be transposed to naphthyl-fused phosphepine, which contrasts with Lammerstma's  3 , 3-P-diphenylphosphepine which acted as heterobidentate phosphane-olefin ligands, due to the presence of a double bond with an olefinic character.[14] To modify the nature of the heteroatom within a -extended-heteropine, we decided to use the Ni-mediated coupling strategy for the synthesis of group 14 containing heteropines. After various unsuccessful tests with silane derivatives, we developed a synthetic strategy toward naphthyl-fused germepines (Scheme 1 and 4). First, a lithiation was realized on the 1,8-dibromonaphthalene. Then, the lithiated compound was reacted with phenyltrichlorogermane leading to the formation of the 13. Despite the presence of broad signals in 1 H NMR, this compound was unambiguously characterized by its crystallographic structure (Figure 3). The treatment with KOH allowed obtaining the intermediate 14 with a Ge-O-Ge bond. [START_REF] Mastroianni | The formation of such Ge-O-Ge bond has already been described[END_REF] Finally, 14 was reacted in the Yamamoto conditions (2 equivalent of Ni(COD)2, COD and 2,2-bipyridine) to afford 15 with good yields (60%) (Scheme 3). This compound is composed of two naphthyl-fused germepines linked through a Ge-O-Ge bond.

Scheme 4. Synthesis of 15

The fluxional character observed in NMR for 13 can be explained by the presence of interconverting rotamers around the germanium atom at room temperature as already observed for B-and P-analogues. [6], [8] Indeed, the 1 H NMR signals sharpened upon cooling to 223K (Figure S6). Moreover, the chemical stability of the chlorogermane 13 can be explained by the steric protection afforded by the bulky bromonaphthyl and in particular the presence of short distances between the peri-substituted Br and Ge (3.104 Å<dGeBr< 3.262 Å; dVdW(Ge-Br) = 3.96 Å, Figure 3). The same behaviour was observed with the phosphine oxide 1. [8] Figure 3. Depictions of the X-ray crystal structures of 13 with zoom on the Ge environment with measured Ge-Br distances (red dotted line) (right).

The optical properties of all compounds were investigated in dichloromethane (C = 10 -5 M). The absorption spectrum of the naphthyl-fused phosphepine 3 consists of a large band (λabs = 346 nm) associated with a -* transition. [8] The compound also displays a blue luminescence centered at 446 nm. First, the impact of P-functionalization was investigated with the cationic phosphepine 9 and complexes 10-12. The optical properties (both absorption and emission spectra) of these compounds are similar to those of phosphepine oxide 3 (see Figure S13). Hence, we already showed that the phosphorus atom is not involved in the MOs linked with the -* transitions, which explains the weak impact on the optical properties of the modification performed at the phosphorus atom. [8] Such behavior was also observed on -extended phosphepine with different backbone. [16] Then, the impact of the molecular structure between phosphocine 2 and phosphepine 3 was investigated. Phosphocine 2 displays an absorption band in the UV region centered at 304 nm. (Fig. 4, Table 1). Compared with phosphepine 3, the insertion of an oxygen atom leads to a hypsochromic shift of 42 nm (abs(2): 304 nm and abs(3): 346 nm). This observation is in accordance with the disruption of the conjugation induced by the presence of the O-atom within the -framework together with the large angle between the two naphthalenes (121.9°, Fig. 1). Despite this conjugation disruption, compound 2 also displays a luminescence centered at 355 nm which is hypsochromically shifted by 91 nm compared to the emission of compound 3 (em = 446 nm). Furthermore, a smaller Stokes shift ((2): 4726 cm -1 < (3): 6480 cm -1 ) is observed for compound 2 indicating a smaller reorganization in the excited state. These observations show that the emission properties originates mainly from the substituted naphthalenes. [17] Figure 4. UV-vis absorption (continuous line) and emission (dot line) of 2 (Green) and 3 (Blue) in diluted DCM (C = 10 -5 M)

To further study the impact of the heteroatom insertion within the heteropine scaffold, the phosphepine 3 and the germepine 15 UV-Vis absorption and fluorescence spectra were compared (Figure 4). Germepine 15 displays an absorption band in the UV region (max [START_REF] Mastroianni | The formation of such Ge-O-Ge bond has already been described[END_REF]: 319 nm). The presence of the germanium atom leads to a 27 nm hypsochromic shift in absorption compared to phosphepine 3. A weak bathochromic shift is observed in emission (em(3): 446 nm and em(15): 457 nm). The Stokes shift with Ge is thus increased compared to P ((3): 6480 cm -1 and (( 15): 9466 cm -1 ) which means that there is a stronger reorganization in the excited state for this species. If we compare with the boron analog B (Figure 1), (()= 1360 cm -1 ), [6] there is clearly a link between the heteroatom nature and the Stokes shift. Thus, a longer Heteroatom-C bond (dB-C<dP-C<dGe-C) leads to stronger reorganization in the excited state. [a] In CH2Cl2 (10 -5 M). [b] Quantum yield measured relative to quinine sulfate (H2SO4, 1 N), ref= 0.55.

CONCLUSIONS

In conclusion, the synthesis of various heteropines featuring P or Ge atoms is described (3, 12), as well as the unexpected preparation of a phosphocine (2). The reactivity of the  3 , 3-P-heteropine 4 is similar to classical phosphine, in particular for its coordination chemistry. Then, the germanium analogue of the phosphepine has been synthesized through an unusually stable chlorogermane precursor. The effect of the ring structure (phosphepine vs phosphocine) and of the heteroatom nature (P vs Ge) was studied through optical spectroscopy highlighting that both the ring size and the nature of the main group element impact the absorption and luminescence properties. This study confirms the potential of -extended heteropine for potential optoelectronic applications and paves the way toward the preparation of heavier main group elements containing PAHs. [18]

Experimental Section

All experiments were performed under argon atmosphere using standard Schlenk techniques. Commercially available reagents were used as received without further purification. Solvents were freshly purified using MBRAUN SPS-800 drying columns. Separations were performed by gravity column chromatography on basic alumina (Aldrich, Type 5016A, 150 mesh, 58 Å) or silica gel (Merck Geduran 60, 0.063-0.200 mm). 1 H, 13 C, and 31 P NMR spectra were recorded on Bruker AV III 300 and 400 MHz NMR spectrometers equipped with BBO or BBFO probeheads. Assignment of proton and carbon atoms is based on COSY, NOESY, edited-HSQC and HMBC experiments. 1 H and 13 C NMR chemical shifts were reported in parts per million (ppm) using residual solvent signal as reference. In the NMR description. High-resolution mass spectra were obtained on a Varian MAT 311 or ZabSpec TOF Micromass instrument at CRMPO (Scanmat, UMS 2001). UV-Visible spectra were recorded rt on a VARIAN Cary 5000 spectrophotometer. The UV-Vis, emission and excitation spectra measurements were recorded on a FL 920 Edinburgh Instrument equipped with a Hamamatsu R5509-73 photomultiplier for the NIR domain (300-1700 nm) and corrected for the response of the photomultiplier. Quantum yields in solution were calculated relative to quinine sulfate (H2SO4, 0.1 M), ref= 0.55. 1 and 3 were synthesized according to published procedures. [8] 6-7 were synthesized according to general method A (without addition of water) and their NMR data fit with our previously reported synthesis. [8] CCDC 1913087 (2)-1913089 (10), 1913090 (12), 1974630 (13) contains the supplementary crystallographic data for this paper. These data can be obtained free of charge from The Cambridge Crystallographic Data Centre. method A). 1 (200 mg, 0.37 mmol, 1 eq) and Cu(0) (47 mg, 0.75 mmol, 2 eq) are dissolved in 30 mL of DMF and 1 mL of water is added. Then the reaction is heated to 160°C during 2 day. Then DMF is evaporated and the crude mixture was purified by silica gel chromatography using DCM/AcOEt (1/1) to afford 2 as a white powder (49 mg, 35 %). 1 H NMR (400 MHz, CD2Cl2) δ 9.00 (ddd, 2H, J = 14.5, 7.2, 1.3 Hz, H8), 8.10 (d, 2H, J = 8.2 Hz, H6), 7.81 (d, 2H, J = 8.2 Hz, H4), 7.76 (t, 2H, J = 8.1 Hz, H7), 7.66 (d, 2H, J = 7.7 Hz, H2), 7.53 (t, 2H, J = 7.9 Hz, H3), 1H,Hpara),4H,Hmeta,ortho). 13 C NMR (101 MHz, CD2Cl2) δ 154.85 (d,J = 2.8 Hz,Cq),139.38 (d,J = 121.7 Hz, Cipso), 137.26 (d, J = 6.5 Hz, C8), 135.49 (d, J = 8.0 Hz, Cq), 132.81 (d, J = 3.0 Hz, C6), 130.52 (d, J = 2.9 Hz, Cpara), 129.08 (d, J = 5.5 Hz, Cq), 128.77 (d,J = 13.7 Hz,Cortho),128.30 (d,J = 11.1 Hz,Cmeta),126.99 (C3),126.78 (d,J = 12.8 Hz,C7), 126.58 (d, J = Compound λabs (nm) [a] λem (nm) [a]  (cm -1 ) [a] εmax (L.mol -1 .cm -1 ) [a] Φ [b] (General method B) 2 (80 mg, 0.2 mmol, 1 eq) is dissolved in 6 mL of dry toluene. HSiCl3 (270 mg, 2.0 mmol, 10 eq) is added dropwise and then heated to reflux 1h. The mixture is filtered on alumina under argon and wash with distillated THF. The solvent is evaporated under the schlenk line vacuum and the resulting intermediate 8 9a is dissolved in 10 mL of dry DCM, then MeOTf (98 mg, 0.6 mmol, 3 eq) is added to 0°C. The mixture is stirred at R.T. for 1h30 and finally washed with an extraction H2O/DCM. The organic phase is dried on MgSO4 and the solvent evaporated. A minimun of DCM is used to dissolve the mixture, heptane is added and the flask is put in fridge during 1 night. The next day the solvent is removed to afford 9 as a white powder. (95 mg, η = 91 %).

(General

11.

General method B was used with 2 (80 mg, 0.204 mmol, 1 eq), 5 mL of dry Toluene and HSiCl3 (275 mg, 2.04 mmol, 10 eq). After the phosphorus deprotection, the mixture is dissolved in 10 mL of dry Toluene and Re(CO)5Cl (73 mg, 0.204 mmol, 1 eq) is added. Then the mixture is heated to reflux during 1h30. Finally the compound is dissolved in DCM and filtered on celite. Then heptane is added and the flask is put in the fridge during 1 night. The next day the solvent is removed to afford the compound 11 as a white powder (106 mg, η = 75 %). 12. General method B was used with 2 (60 mg, 0.153 mmol, 1 eq), 5 mL of dry Toluene, HSiCl3 (207 mg, 1.53 mmol, 10 eq) and Pd(CH3CN)Cl2 (18 mg, 1.53 mmol, 10 eq). The compound is dissolved in DCM and filtered on celite. Then heptane is added and the flask is put in the fridge during 1 night. The next day the solvent is removed to afford the compound 12 as a yellow powder (61 mg, η = 97 %). 13. 1,8-Dibromonaphtalene (1.0 g, 3.53 mmol, 2.7 eq) is dissolved in 50 mL of dry Et2O. The solution is cooled down to -80°C then BuLi (1.41 mL, 3.53 mmol, 2.7 eq) is added dropwise and the solution is stirred for 30 mn at -80°C then 30 mn at rt. The solution is again cooled down to -80°C and PhGeCl3 (120 mg, 0.47 mmol, 1 eq) is added dropwise. The mixture is then stirred at RT overnight. Then the solution is extracted with water and the organic phase is dried on MgSO4 and evaporated. The crude mixture is purified by silica gel chromatography using DCM/C7 (1/1). The compound is dissolved in a minimum of DCM and heptane is added. The flask is put in the fridge during 1 night. The next day the solvent is removed to afford the compound 13 as colorless crystals (0.580 mg, η = 79%). 1 H NMR (400 MHz, CD2Cl2, 223K) δ 8. 83 -8.68 (m, 1H), 8.05 -7.86 (m, 5H), 7.79 -7.70 (m, 2H), 7.67 -7.56 (m, 3H), 7.48 -7.28 (m, 6H). 13 C NMR

Figure 1 .

 1 Figure 1. Top (left), lateral (center) and back (right) crystallographic views of 2 (a) and 3 (b).

Figure 2 .

 2 Figure 2. Crystallographic structures of 10 (left) and 12 (right) and zoom on the metal environments (Bottom).

Figure 4 .

 4 Figure 4. UV-vis absorption (continuous line) and emission (dot line) of 3 (blue) and 15 (Orange) in diluted DCM (C = 10 -5 M)

Table 1 :

 1 Photophysical data.

  General method B was used with 2 (60 mg, 0.153 mmol, 1 eq), 5 mL of dry toluene, HSiCl3 (207 mg, 1.53 mmol, 10 eq) and Me2SAuCl (45 mg, 0.153 mmol, 1 eq). The compound is dissolved in DCM and filtered on celite. Then heptane is added and the flask is put in the fridge during 1 night. The next day the solvent is removed to afford the compound 10 as a white powder (64 mg, η = 71 %).

	1 H NMR (400 MHz, CD2Cl2) δ 8,38 (dt, 2H, J = 8.2
	Hz, J = 1.6 Hz, H6), 8.09 (m, 4H, H8 et H2or4), 7.79 (m, 2H, H7), 7.73 (t, 2H, J = 7.7 Hz H3), 7.63 (m, 1H, Hpara), 7.58 (m, 2H,
	H2or4), 7.45 (m, 2H, Hmeta), 7.21 (m, 2H, HOrtho), 2.64 (m, 3H, H13). 13 C NMR (101 MHz, CD2Cl2) δ 138.4 (d, JC-P = 2.9 Hz, Cq),
	138.2 (s, C2or4), 137.3 (d, JC-P = 3.4 Hz, C6), 136.4 (d, JC-P = 9.6 Hz, C2or4), 135.0 (d, JC-P = 3.0 Hz, Cpara), 134.3 (d, JC-P = 10,4
	Hz, Cq), 132.9 (d, JC-P = 9.1 Hz, Cq), 132.3 (d, JC-P = 10.7 Hz, Cortho), 131.2 (d, JC-P = 1.6 Hz, C8), 130.4 (d, JC-P = 13.1 Hz, Cmetha),
	128.6 (s, C3), 126.2 (d, JC-P = 14.5 Hz, C7), 122.9 (d, JC-P = 91.6 Hz, Cipso), 114.8 (d, JC-P = 86.3 Hz, C9), 12.6 (d, JC-P = 61.3 Hz,
	C13). 19 F NMR (376 MHz, CD2Cl2): δ -79.9 (s) 31 P NMR (162 MHz, CD2Cl2) δ + 23.7. HRMS (ESI, CH3OH / CH2Cl2: 90/10)
	M + (C27 H20 P) : m/z Calculated : 375.12971, m/z Found : 375.1298.
	10. 1 H NMR (400 MHz, CD2Cl2) δ 8,82 (ddd, 2H, J = 21.6 Hz, J = 6.9 Hz, J = 1.3 Hz, H8),
	8.13 (d, 2H, J = 8.3 Hz, H6), 7.90 (d, 2H, J = 8.1 Hz, H2or4), 7.68 (t, 2H, J = 6.8 Hz H7), 7.50 (t, 2H, J = 7.6 Hz, H3), 7.34 (d, 2H,
	J = 7.4 Hz, H2or4), 7.07 (m, 1H, Hpara), 6.93 (m, 2H, Hmeta), 6.54 (m, 2H, HOrtho).

13

C NMR (101 MHz, CD2Cl2) δ 140.9

(d, C8), 139.3 (d, Cq), 136.6 (s, C2ou4)

, 134.7 (d, JC-P = 2.9 Hz, C6), 134.4 (d, JC-P = 7.1 Hz, Cq), 133.8 (d, JC-P = 60,4 Hz, Cipso), 133.7 (d, JC-P = 3.4 Hz, Cq), 130.9 (d, JC-P = 12.7 Hz, Cortho), 130.5 (d, JC-P = 2.6 Hz, Cpara), 130.3 (d, JC-P = 0.9 Hz, C2or4), 128.5 (s, Cmeta), 127.3 (s, C3), 125.3 (d, JC-P = 17.9 Hz, C7), 124.1 (d, JC-P = 60.1 Hz, C9). 31 P NMR (162 MHz, CD2Cl2) δ + 45.7. HRMS (ESI, CH3COCH3) [M+Na + ](C26 H17 35 Cl Na P Au) : m/z Calculated : 615.03142 m/z Found : 615.0316.

  1 H NMR (400 MHz, CD2Cl2) δ 8.80 (q, 4H, J = 8.2 Hz, H8), 8.10 (t, 4H, J = 8.2 Hz, H6), 7.92(d, 4H, J = 8.0 Hz, H7), 7.71 (t, 2H, J = 7.5 Hz, H2or4), 7.53 (t, 4H, J = 7.6 Hz, H7), 7.38 (d, 4H, J = 7.4 Hz, H2or4), 7.12 (t, 2H, J = 8.1 Hz, Hpara), 7.01 (t, 4H, J = 7.6 Hz, Hmeta), 6.81 (m, Hortho).13 C NMR not measured for solubility reasons 31 P NMR (162 MHz, CD2Cl2) δ + 36.2.HRMS (ESI, CH3COCH3) [M+Na + ](C52 H34 Cl2 Na P2 Pd) : m/z Calculated : 921.0444, m/z Found : 921.0439.

ACKNOWLEDGMENTS

This work is supported by the Ministère de la Recherche et de l'Enseignement Supérieur, the CNRS, the Région Bretagne, the French National Research Agency (ANR Heterographene ANR-16-CE05-0003-01).