The Science: Technical Overview
Technical Overview of Lpath's Core Technology
Bioactive lipids as drug targets
Lpath is the category leader in lipid-based therapeutics, an emerging field of medical science whereby bioactive signaling lipids are targeted for treating important human diseases.
It was not long ago that certain lipids were determined to be bioactive in nature and therefore bona fide targets for rational drug design. It is now appreciated by key opinion leaders that changes in lipid metabolism can lead to cancer, diabetes, neurodegenerative disorders, immune function, pain, mental disorders, ocular disorders, and inflammation. Scientists believe that there are over 1,000 members of the functional lipidome, opening up a sizeable array of new potential targets for therapeutic interventions.
Lpath has two distinct advantages in this emerging field of lipid-based therapeutics:
- Because lipids are extremely small (~1/100 the size of proteins, on average) and are not water-soluble, they are challenging to study. Many of the tools that were developed over decades to analyze proteins simply do not work with lipids. Lpath was one of the first to recognize that bioactive lipid signaling molecules, like sphingosine-1-phosphate (S1P) and lysophosphatidic acid (LPA), were valid targets; as such, over the last 10+ years, we have developed a sophisticated repertoire of proprietary processes, know-how, and assays that enable us to study and analyze the performance characteristics of these challenging molecules.
- Lpath is the only company that has been successful in generating and advancing therapeutic antibodies against bioactive lipids. Using our proprietary ImmuneY2™ drug-discovery engine, we have now done it several times over, and we continue to apply our technology to new bioactive lipid targets.
Lpath has further widened the lead over the competition by submitting patent applications that the company believes will provide protection of several key aspects of the platform technology.
Sphingosine-1-phosphate (S1P), an important bioactive lipid
Sphingosine-1-phosphate (S1P) is a bioactive lipid that is a key component of the sphingolipid signaling cascade. S1P acts on a complement of five G-protein Coupled Receptors (GPCRs) to promote cell proliferation, migration, and protection from cell death (apoptosis). In pathological conditions, S1P has many actions that can promote inflammation, pathogenic fibrosis and dysregulated angiogenesis.
Schematic of Sphingosine-1-Phosphate
Lpath's antibody against S1P, Sphingomab™
Lpath has produced and optimized a monoclonal anti-S1P antibody (Sphingomab). After demonstrating proof-of-concept with Sphingomab in various animal models of cancer and AMD, Lpath then humanized the anti-S1P antibody. The humanized version of the antibody demonstrates the same selectivity and specificity, with picomolar affinity, as Sphingomab and can similarly absorb S1P from the extracellular fluid, thereby lowering the effective concentration of S1P.
The ocular formulation of humanized Sphingomab is called iSONEP™, while the systemic formulation is known as ASONEP™.
iSONEP in wet AMD (also called exudative AMD)
Wet AMD (Age-related Macular Degeneration) is the leading cause of blindness in the U.S. and currently affects more than 1.6 million people). There are estimated to be 2-3 times this many cases worldwide. According to the NIH's National Eye Institute, the number of AMD sufferers in the U.S. is projected to increase from about 1.6 million to 2.9 million by 2020.
Despite the epidemic of vision loss caused by wet AMD, only a few therapies can slow the progression of the disease. Currently favored therapeutic modalities include Eylea®, Lucentis® and off-label use of Avastin®, all of which target a single growth factor, VEGF, and appear to exert most of their beneficial effects via an anti-permeability action (i.e., an anti-leaky effect on the leaky lesion, often referred to as the CNV, resulting in resolution of intra- and sub-retinal edema; these drugs typically do not cause any reduction in the lesion itself. Wet-AMD-related vision loss, however, is not due solely to CNV-induced edema. Pathologic disruption and remodeling of the retinal and subretinal architecture caused collectively by CNV, sub-retinal fibrosis, edema, and inflammation result in the loss of visual acuity associated with wet AMD. These multiple causes of retinal injury are not addressed by currently available treatments. Thus, agents having the ability to treat the multiple mechanisms that underlie wet-AMD-related vision loss, beyond just treating vascular leakiness, would be of great value and are likely to fulfill the unmet medical need associated with wet AMD
Growing evidence suggests that S1P could contribute to both the early and the late stages of maladaptive retinal remodeling associated with wet AMD. S1P has a pronounced non-VEGF dependent pro-angiogenic effect. S1P also stimulates migration, proliferation, and survival of multiple cell types, including fibroblasts, endothelial and inflammatory cells that participate in the multiple maladaptive processes of wet AMD. S1P is also linked to the production and activation of VEGF, FGF, PDGF MCP-1 IL-6, IL-8 and other growth factors implicated in the pathogenesis of wet AMD. Inhibiting the action of S1P could therefore be an effective therapeutic treatment for wet AMD that may (i) offer significant advantages over exclusively anti-VEGF approaches or (ii) act synergistically with them to address the complex processes and multiple steps that ultimately lead to significant visual loss.
In several independent models of CNV, Sphingomab™, and its humanized counterpart iSONEP™, demonstrated the following:
- Marked reduction of retinal neovascularization and vascular leakage.
- Marked reduction of inflammation, including macrophage recruitment.
- Substantial decrease in collagen scar formation (fibrosis).
The compelling results of these studies suggest that iSONEP™ can inhibit the vascular and extravascular components of not only wet AMD, but also ischemic retinopathies such as diabetic retinopathy. In addition, the anti-fibrosis and anti-inflammatory data suggest iSONEP™ can be efficacious in disorders such as proliferative retinopathy, glaucoma (where trabectulectomy is performed), and various anterior-segment diseases.
ASONEP in cancer
S1P promotes tumor growth by stimulating cell proliferation, metastasis, and cell survival. Recent studies indicate that S1P also promotes tumor angiogenesis by supporting the migration and survival of endothelial cells when they form new vessels within tumors. Importantly, sphingosine kinase (SPHK), the enzyme responsible for S1P production, is an oncogenic protein, further demonstrating that S1P is a potential therapeutic target for cancer.
As discussed above, Lpath has successfully generated murine and humanized monoclonal antibodies that bind to and inhibit this tumorigenic, pro-inflammatory, fibrogenic and pro-angiogenic growth factor; the murine version of the antibody is called Sphingomab, and the systemic formulation of this humanized antibody is called ASONEP.
We hypothesize that this antibody could be used as a therapeutic molecular sponge to selectively absorb S1P, thus lowering the effective extracellular concentrations of this tumor-facilitating factor. It is anticipated that this would result in the reduction of tumor volume and metastatic potential, as well as the simultaneous blockage of new blood vessel formation that would, otherwise, feed the growing tumor. In addition, we hypothesize that the ability of S1P to protect cells from apoptosis could be reversed by the antibody, thus increasing the efficacy of standard pro-apoptotic chemotherapeutic agents.
Some of the key attributes of this anti-S1P antibody are discussed below:
- The antibody is highly specific to S1P. It does not appreciably cross react with other structurally similar bioactive lipid mediators, including sphingosine (SPH), sphingosylphosphorylcholine (SPC) or lysophosphatidic acid (LPA).
- Utilizing BIAcore technology, the affinity of Sphingomab for S1P is much higher than most therapeutic antibodies, particularly other molecular sponges.
- Many in vitro studies have now shown that S1P is a tumorigenic growth factor for several human cancer cell lines and that S1P has profound ability to activate many different types of fibroblasts and inflammatory cells. Lpath has data demonstrating compelling in vivo efficacy in cancer treatment of animals, as follows:
- Sphingomab significantly reduced tumor volumes and weights in human models of lung cancer in mice where human cancer cells are xenografted into mice, including ovarian, breast, lymphoma, myeloma, lung and melanoma cancers.
- Sphingomab significantly reduced tumor angiogenesis (new blood vessel formation) in the in vivo mouse Matrigel plug assays, in xenograft models as well as several in vitro assays.
- Sphingomab significantly reduced circulating levels of the pro-angiogenic growth factors, VEGF, IL8, and IL6 in tumor mice. In cell culture, the ability of cancer cells to release these growth factors is reduced by Sphingomab. Taken together, it appears that VEGF and other angiogenic factors may require S1P for them to exert their full activity.
- In vivo, the antibody significantly reduced tumor-associated angiogenesis in well-established murine models.
- In vivo, the antibody significantly reduced tumor progression in murine models of human cancers.
- For details on much of the in vitro and in vivo work, please see the following publication:
Visentin, B., Vekich, J., Sibbald B., Moreno, K., Cavalli, A., Garland, W., Lu, Y., Mills, G. and Sabbadini, R. (2006) Validation of an anti-sphingosine-1-phosphate antibody as a potential therapeutic in reducing growth, invasion, and angiogenesis in multiple tumor lineages. Cancer Cell, Volume 9, Issue 3 March 2006, 225-238. www.cancercell.org
Lysophosphatidic Acid (LPA)
Lysophosphatidic acid (LPA) is a key extracellular signaling mediator that has been linked to neuropathic pain, cancer, and fibrosis (pulmonary, renal, and liver fibrosis). In animal models, receptor-mediated LPA signaling is crucial in the initiation of neuropathic pain and in pathologic fibrosis. In addition, LPA1-receptor activation has been shown to stimulate macrophage recruitment and connective-tissue growth-factor expression.
Schematic of Lysophosphatidic Acid
Lpathomab™ (antibody against LPA)
Lpath has developed monoclonal antibodies that specifically recognize LPA with the aim of lowering the effective extracellular levels of LPA. In CNS disease, it is anticipated that neutralizing LPA would result in significant neuroprotection and in fibrosis, neutralizing LPA appears to decrease collagen deposition and inflammation.
- Lpath has successfully generated several monoclonal antibodies to LPA.
- The antibodies are highly specific to LPA; they do not appreciably cross react with other structurally similar bioactive lipid mediators, including S1P, ceramide (CER), sphingosine (SPH), sphingosylphosphoryl choline (SPC), lysophosphatidyl choline (LPC), or other bioactive lipids.
- Lpath's antibodies to LPA have also shown prophylactic and intervention effects in animal models of neuropathic pain, diabetic neuropathy and traumatic brain injury.
- Lpath has data suggesting that antibodies to LPA could have an effect in animal models of renal and pulmonary fibrosis.
- Lpath has data demonstrating in vivo efficacy of our antibodies against LPA in animal models of human cancer, including significant reduction of vasculature in tumors, reduction of cytokine levels in tumor-bearing mice, and reduction of metastatic cancer.
- The anti-angiogenic effects of our antibodies against LPA were also observed in the murine choroidal neovascularisation model of wet AMD.