Archives par mot-clé : anti-VEGF

Ophthotech attaque la DMLA sur tous les fronts

Si les médicaments anti-angiogéniques actuels ont tous le même but (se lier au VEGF afin d’empecher la liaison à ses récepteurs), Ophthotech a dans son pipeline trois molécules qui s’attaquent à d’autres cibles :

  • Suite à un accord de licence avec Biogen Idec et PDL BioPharma, ils développent le volociximab (M200) en ophtalmologie :

    Volociximab is an investigational monoclonal antibody targeting α5β1 integrin, a key protein involved in the formation of blood vessels, a process known as angiogenesis. […] “α5β1 integrin is a critical survival factor for proliferating endothelial cells involved in angiogenesis,” said Samir Patel, MD, president and CEO of Ophthotech. « The preclinical studies to date provide very strong support for developing volociximab for ophthalmic indications. It represents a potential breakthrough for the treatment of AMD.”

    Source : OphthalmologyWeb

  • Un aptamer anti-PDGF (E10030) entre en phase I, afin d’étudier sa tolérance en combinaison avec un anti-VEGF :

    Platelet-derived growth factors (PDGFs) and their receptors are critical targets in anti-angiogenic therapy. PDGF plays a significant role in angiogenesis and has been implicated in ocular neovascularization. The activities of PDGF and VEGF in the initiation of angiogenesis and mediation of blood vessel growth and behavior are independent of each other, suggesting that concurrent inhibition could lead to superior efficacy in treating neovascularization.

    Platelet-derived growth factor B (PDGF-B) is implicated in vascular stability and function through its role in activating the recruitment of mural cells (pericytes) by endothelial cells to envelop the developing vasculature. Pericyte recruitment is part of the maturation process in blood vessel development and pericytes act as support cells for mature blood vessels. Once the mural cell population is well established, the effectiveness of anti-VEGF agents is greatly reduced. It is possible that disruption and stripping of mural cell recruitment by an anti-PDGF agent could potentiate the efficacy of an anti-VEGF attack by causing neovascular regression. Therefore, combination therapy in wet AMD with anti-VEGF and anti-PDGF agents could represent breakthrough therapy.

    E10030, an aptamer-based compound directed against PDGF-B, is being developed for the potential treatment of wet AMD. E10030 is a pegylated aptamer containing 32 monomeric units (32-mer) arranged as a linear sequence of three oligonucleotide segments connected by non-nucleotide hexaethylene glycol spacers. The aptamer terminates in a hexylamino linker to which two 20-kilodalton monomethoxy polyethylene glycol units are covalently attached via the two amino groups on a lysine residue.

    Pharmacology studies indicate that E10030 binds to PDGF-B with high specificity and affinity and inhibits the functions of PDGF-B both in vitro and in vivo. In pre-clinical studies, E10030 demonstrated the potential to regress neovascularization when used in combination with a VEGF-A inhibitor. In experiments involving models of ocular vascularization [1], concurrent inhibition of PDGF-B and VEGF-A signaling was superior to inhibition of the VEGF-A pathway alone. The combined treatment was able to induce the regression of existing vessels, compared to inhibition of VEGF-A alone. Findings from a corneal neovascularization model demonstrated that pericytes were stripped from newly growing vessels, but not from existing limbal vessels. This evidence suggests that combined administration of an anti-PDGF-B agent with an anti-VEGF agent may result in regression of abnormal blood vessels in neovascular AMD while preserving the normal vascular architecture. Therefore, combination therapy with a regimen incorporating an anti-PDGF agent with an anti-VEGF agent holds great promise for enhanced efficacy in wet AMD.

    Source : OSN

  • En parcourant leur site internet, on trouve aussi que la voie du complément n’est pas oubliée, avec un aptamer anti-C5 (ARC1905) :

    Evidence for complement-mediated inflammation in AMD is further reinforced by genetic linkage and association studies which suggest that approximately 50 to 75% of AMD cases have polymorphism in complement regulatory proteins compared to age-matched controls. […]
    Anti-C5 aptamer ARC1905 is a potent and specific inhibitor of complement activation. ARC1905 is a pegylated RNA aptamer. ARC1905 inhibits C5, a central component of the complement cascade, which plays multiple roles in innate immunity and inflammatory diseases. Inhibition of this key step in the complement cascade at the level of C5 prevents the formation of key terminal fragments (C5a and C5b-9) regardless of which pathway (alternate, classical or lectin) induced their generation. The C5a fragment is an important inflammatory activator inducing vascular permeability, recruitment and activation of phagocytes. C5b-9 is involved in the formation of membrane attack complex (MAC: C5b-9) which initiates cells lysis. By inhibiting these C5-mediated inflammatory and MAC activities, therapeutic benefit may be achieved in both dry as well as wet AMD.

DMLA et accidents thrombo-emboliques (AVC, infarctus)

Les résultats à un an de l’étude SAILOR et une étude parue dans le British Journal of Ophthalmology apportent de nouveaux éléments quant au risque d’accidents thrombo-embolique des patients atteints de DMLA :

  1. Alors que l’analyse intermédiaire (à 6 mois) de SAILOR faisait craindre une augmentation du risque d’AVC sous Lucentis (notamment pour les patients ayant déjà des antécédents d’accidents de ce type), les données à un an, communiquées récemment, sont plutôt rassurants, avec certes toujours une « tendance » à une incidence supérieure d’AVC sous Lucentis 0.5 mg par rapport à 0.3 (1.2% vs 0.7%), mais la différence n’est pas statistiquement significative (p=0.21) :

    One-year data on the phase 3b SAILOR (Safety Assessment of Intravitreal Lucentis for AMD) trial showed the drug was safe and was not associated with higher rate of stroke, according to principal investigator David S. Boyer, MD, at Bascom Palmer Eye Institute’s Angiogenesis, Exudation, and Degeneration 2008 meeting in Key Biscayne, Florida.

    The study included approximately 4,300 patients with all subtypes of new or recurrent active subfoveal wet age-related macular degeneration (AMD) who were treated with 0.3 mg or 0.5 mg doses of intravitreal ranibizumab (Lucentis, Genentech). Results were based off of information gathered from cohort 1, which included 2,378 patients.

    These data come almost 1 year after Genentech issued a letter to physician-users (a so-called « Dear Doctor » letter) in January 2007, noting safety concerns in the interim safety analysis of SAILOR. That preliminary data showed a four-fold difference in the rate of strokes in the group receiving the 0.5-mg (1.2%) than in the group receiving the 0.3-mg dose (0.3%) at an average follow-up of 230 days. Patients with previous history of stroke appeared to be at higher risk for stroke during the trial.

    One-year results, however demonstrated that although the US Food and Drug Administration (FDA) approved dose of Lucentis (0.5 mg) trended toward a higher incidence of stroke (1.2% vs. 0.7% in the 0.3 mg dose group) the results were not statistically significant (P=.21). The stroke rate in the general US population (65 years of age or older) is 1.4%, according to Anne E. Fung, MD, who presented at the same meeting on the rates of arterial thromboembolic events in Medicare patients.

    « I think that we over-analyzed the 6-month data; perhaps it was blown a bit out of proportion in comparison to all of the other studies out there at the time, » Dr. Boyer said in a telephone interview with Retina Today. « Genentech reported the 6-month data, as it should have. But I think that [the results of SAILOR] are one of the reasons you wait for a year to get the complete data. We now see that there was no probable statistical significance — the numbers just caught up by the end of the trial. If we examined the data for a longer period of time, those numbers for the two dosing groups might even come closer in line to each other. »

    As SAILOR was a 1-year study, there are no further plans to continue the trial, Genentech spokeswoman Krysta Pellegrino told Retina Today. Results for the second SAILOR cohort (approximately 1,900 patients), however, will be available sometime this year.

    Sur, il est précisé que cette tendance (9.6% vs 2.7% quand même !) est également observée dans le sous-groupe de patients aux antécédents d’AVC, mais qu’il est difficile de conclure en raison du faible nombre d’évènements :

    At one-year, patients with a prior history of stroke had a higher rate of stroke in the 0.5 group (9.6%) compared to the 0.3 group (2.7%). However, this trend was inconclusive, as the number of events was small. These data are consistent with epidemiologic data showing that prior history of stroke predisposes patients to subsequent stroke.

  2. Dans une publication en ligne depuis le 29 février, basée sur les examens de patients 10 ans après leur inclusion dans la Blue Mountain study, les sujets de moins de 75 ans avec des signes de maculopathie liée à l’âge à l’inclusion ont un risque de décéder par AVC ou infarctus du myocarde à 10 ans multiplié par 2, par rapport aux patients sans signe de DMLA.
    Pour ceux qui avaient déjà à l’inclusion des signes de DMLA compliquée, le risque est multiplié par 5 (infarctus du myocarde) à 10 (AVC).

    Background/aims: Age-related macular degeneration (AMD) and vascular disease share similar risk factors. Recent data suggest AMD may independently predict stroke or coronary heart disease. We prospectively assessed the relationship between AMD and risk of stroke- or cardiovascular-related death in an Australian population.
    Methods: Of 3654 baseline participants (1992-4) aged 49+years, 2335 were re-examined after 5-years and 1952 after 10-years. Retinal photographs were graded using the Wisconsin System. History and physical examination provided data on possible risk factors. Deaths and cause of death were confirmed by data linkage with the Australian National Death Index. Risk ratios (RR) were estimated in Cox models.
    Results: Among persons aged <75 years at baseline, early AMD predicted a doubling of cardiovascular mortality (RR, 2.32; 95% confidence interval (CI), 1.03-5.19), over the next decade, after controlling for traditional cardiovascular risk factors. Late AMD predicted 5-fold higher cardiovascular mortality (RR, 5.57; CI, 1.35-22.99) and 10-fold higher stroke mortality (RR, 10.21; CI, 2.39-43.60) after adjusting for age and sex only. These associations were not present when persons older than 75 were included. Conclusion: AMD predicted stroke and cardiovascular events over the long-term in persons aged 49-75 years. This may have potential implications for new intravitreal anti-VEGF AMD therapies. Tan JS, Wang JJ, Liew G, Rochtchina E, Mitchell P. Age-related macular degeneration and mortality from cardiovascular disease or stroke. Br J Ophthalmol. 2008 Feb 29 [Epub ahead of print]

Donc, chez les patients traités par anti-VEGF pour DMLA exsudative, il semble que la probabilité de décéder d’un AVC ou d’un infarctus du myocarde soit plus du fait de facteurs de risques partagés entre DMLA et pathologies cardio-vasculaires, que d’un traitement anti-VEGF…
Mais, en raison du (finalement) faible nombre d’évènements, il faudra probablement attendre d’avoir un peu plus de recul pour conclure de manière formelle…

Source : Retina Today eNews

Anti-VEGF : Molécules et Mécanismes (JIFRO, 31 janvier 2008)

Un an après en avoir déjà parlé, voilà une mise à jour concernant les stratégies anti-VEGF et anti-angiogéniques utilisées en ophtalmologie, présentée au cours des premières Journées Interactives de Formation de Réalités Ophtalmologiques (JIFRO) :

Ces fichiers sont à votre disposition pour une utilisation personnelle (consultation) :
aucun élément ne peut être diffusé sans mon autorisation.
N’hésitez pas à me contacter pour toutes questions.

Pour plus de détails, vous pouvez vous référer à une revue de la littérature parue à la même période : Utilisation des anti-VEGF dans la dégénérescence maculaire liée à l’âge. Fajnkuchen F et Cohen SY. J Fr Ophtalmol 2007 Jan;31(1):94-110.

Disponibilité de l’Avastin : accord entre Genentech et ophtalmologistes américains

En cette période de « trêve des confiseurs« , un accord semble avoir été trouvé entre Genentech (le fabriquant de Lucentis et Avastin) et ophtalmologistes américains, qui permettra donc à ces derniers de continuer à s’approvisionner en Avastin.

Les ophtalmologistes pourront en effet le commander directement auprès de grossistes, qui livreront le médicament, au choix, soit à une pharmacie hospitalière, soit à une « compounding » pharmacie, soit au praticien lui même.

Bien que la mise en place de cette « filière » puisse varier selon les états, cette décision marque donc un signe de bonne volonté du laboratoire pour permettre l’accès à l’Avastin.

Source : OSN, New York Times.

En savoir plus :

Anti-VEGF par Pierre Corvol

Les anti-VEGFs sont une avancée dans le traitement de la DMLA, et il en est souvent question ici…
Afin d’en savoir plus, je ne peux que vous inciter à écouter les cours donnés sur le sujet par Pierre Corvol au Collège de France en 2006.

Au sommaire :

  • De l’hypothèse à la preuve du concept, Angiogenèse normale et tumorale
  • Facteur de croissance de l’endothelium vasculaire
  • La preuve du concept, Le VEGF
  • Normalisation des vaisseaux tumoraux par les anti-VEGF
  • Relations intimes entre oxygénation et tumorigenèse
  • Respiration de la mitochondrie, oxygénation cellulaire et cancer