Antagonists of cannabinoid receptor 1 (CB1) have the potential to treat several metabolic diseases including obesity and fatty liver disease. Recently, rimonabant and other developed CB1 antagonists were withdrawn from the market because of the observed adverse effects on the central nervous system (CNS).

Studies clearly showed that rimonabant is well absorbed and has a high BBB permeability. Thus, reduced BBB or decreased rimonabant penetration into the brain is a crucial issue to overcome the CNS side-effects. For such a purpose rimonabant was entrapped in polymeric nanoparticles (NPs), able to release such a lipophilic drug  in a controlled manner while circulating in the vasculature, prolong its apparent biological half–life and deliver the drug to a specifically targeted organ while minimizing the passage through the BBB.

The preliminary data of rimonabant encapsulation in polymeric nanoparticles showed encouraging results for the encapsulation of small amounts of rimonabant, but when we attempted to increase the drug content within the NPs the drug loading efficiency decreased. Thus, there is a clear need to modify the lipophilicity and solubility properties of the molecule. Modification of rimonabant into a higher lipophilic molecule was performed to facilitate incorporation into the polymeric nanoparticles.

It is believed that such an approach will improve rimonabant prodrug encapsulation within polymeric nanoparticles enabling efficient drug loading without escape or release of the prodrug into circulation, thus preventing its penetration into the brain. Once the prodrug-loaded NPs reach the target organ following controlled biodegradation of the NPs and progressive release of the prodrug, appropriate enzymatic cleavage of the ester bond will result in the formation of active rimonabant able to elicit an adequate local peripheral therapeutic activity and thus overcome the CNS side-effects. 
 

Keywords: Bone Marrow Transplantation, Graft versus Host Disease, hematopoiesis, THC, CBD

Bone Marrow Transplantation (BMT) is a well-established treatment for malignant and non-malignant hematological diseases. Allogeneic transplantation comes with the risk of Graft versus Host Disease (GVHD), a major cause of morbidity and mortality in BMT patients. In addition, the toxicity of the conditioning protocol which precedes BMT impairs innate and adaptive immunity, making transplanted patients very susceptible to both common and unusual infections.

In the past few years, numerous publications have reported the potential of cannabis-based medicines for the treatment of various conditions. Among the patients who can benefit from such treatment are BMT patients, who often suffer from nausea and chronic pain.

Cannabis contains more than 60 chemical compounds classified as cannabinoids.  In addition to their effect on the nervous system, cannabinoids also impart important immunological effects. Although a lot of information has been gathered regarding the influence of cannabinoids on the immune response, the effect of these drugs on rehabilitation of the hematological system after BMT and their efficacy in GVHD patients is largely unknown. Cannabis treatment was shown to reduce GVHD in a mouse model that did not include BMT and a recent publication demonstrated the beneficial effect of the cannabinoid CBD in GVHD patients, but other cannabinoids were not examined.

We hypothesize that cannabinoids have a selective effect on hematopoietic and immune cells and therefore different cannabinoids would have different effects on hematopoiesis and on GVHD. In our study we aim to provide data about the influence of different cannabinoids on hematopoiesis and as GVHD therapy after BMT. We use both in vivo and in vitro models to test the effect of cannabinoid treatment (CBD, THC and cannabis extracts) on immune activation, on rehabilitation of the hematologic system after BMT and on the clinical condition of mice with GVHD.

Our preliminary results demonstrate some of the effects of cannabis extract and cannabinoids on immune activation and on rehabilitation of hematological cells after BMT.

A better understanding of the effects of different cannabinoids on hematological reconstitution and GVHD pathology will allow the use of specific cannabinoid drug for each individual patient: as personalized medicines.

Multi-targeted single molecules have many advantages over multiple agents such as “drug cocktails”, linked drugs and others. In order to design in silico multi-targeted agents there is a need to provide models based on ligands, or based on protein targets’ structures, or both ¹. There are many possible combinations of requirements for targets and anti targets concerning agonists and antagonists of CB1 and CB2 in the CNS and in the periphery.

Peripheral treatment with a CB1 antagonist reduced food intake and body weight ². Selective CB2 activation may serve therapeutic manipulation of untoward immune responses including those associated with a variety of neuropathies that exhibit a hyper-inflammatory component ³ (devoid of psychoactive effects of CB1 activation).

Combination of targeting specific receptors as well as anti-targets, could be achieved using our in-house Iterative Stochastic Elimination (ISE) Algorithm⁴ for constructing activity models of the cannabinoid receptors. ISE models are based on the idea of classification but provide an ensemble of filters of molecular properties that enable the quantification of each molecule’s chances due to the differences in classification ability between filters. These models will form the basis for subsequent virtual screenings of huge libraries of commercially available molecules to filter candidates that will be purchased and tested⁵. Thus, ISE models serve to discover new multitargeting candidates.

 * Molecular Modeling and Drug Discovery Lab, Institute for Drug Research, The Hebrew University of Jerusalem, Israel

1. Boran, A. D. W. & Iyengar, R. Systems pharmacology. Mt. Sinai J. Med. 77, 333–44
2. Nogueiras, R. et al. Peripheral, but not central, CB1 antagonism provides food intake-independent metabolic benefits in diet-induced obese rats. Diabetes 57, 2977–91 (2008).
3. Cabral, G. A. & Griffin-Thomas, L. Emerging Role of the CB2 Cannabinoid Receptor in Immune Regulation and Therapeutic Prospects. Expert Rev. Mol. Med. 11, e3
4. Stern N and Goldblum A. Iterative Stochastic Elimination for Solving Complex Combinatorial Problems in Drug Discovery Isr. J. Chem. 54, 1338-67 (2014)
5. Zatsepin M et al. Computational Discovery and Ecperimnetal Confirmation of TLR9 Receptor Antagonist Leads, http://pubs.acs.org/doi/abs/10.1021/acs.jcim.6b00070

Our laboratory developed a unique chemoinformatics classification method for modeling and discovery of novel drug candidates. We transform molecular 2D structures into a large set of physico-chemical properties, and use biological acitivy data from specific websites in order to construct “learning sets” that contain known active molecules which are “diluted” with a large number of inactive molecules. We focus mainly on “ligand based” modeling, which is not dependent on the structure of protein targets and are particularly useful if such target structures are absent¹.

Iterative Stochastic Elimination (ISE)² algorithm was devised to solve combinatorial “explosive” problems with frequently more than 10¹⁰⁰ possible combinations. ISE identifies those variable values that contribute consistently to the worst results, but do not contribute similarly to the best solutions, and eliminates them thus producing a smaller set of variable values and a smaller number of combinatorial options, allowing one to proceed to the discovery of a set of optimal states of the system – an ensemble of filters of molecular properties (calculated by MOE software³, each filter composed of a few (4-5) molecular physicochemical properties and their ranges.  The final set of "best filters" solutions is considered to be a “model”.  For both receptors (CB1 and CB2), We construct models of agonism and of antagonism, each one separately, for both CB1 and CB2, based on resources of data such as ChEMBL⁴. These are used subsequently to score any molecule for its ability to have any type of interaction with CB1 and CB2, and thus to discover novel cannabinoids with specific activities.

 * Molecular Modeling and Drug Discovery Lab, Institute for Drug Research, The Hebrew University of Jerusalem, Israel

1. Li, H. et al. Machine learning approaches for predicting compounds that interact with therapeutic and ADMET related proteins. J. Pharm. Sci. 96, 2838–60 (2007).
2. Stern, N. & Goldblum, A. Iterative Stochastic Elimination for Solving Complex Combinatorial Problems in Drug Discovery. Isr. J. Chem. 54, 1338–1357 (2014).
3. Molecular Operating Environment (MOE), 2012.10; Chemical Computing Group Inc., 1010 Sherbooke St. West, Suite #910, Montreal, QC, Canada, H3A 2R7, 2012.
4. https://www.ebi.ac.uk/chembl/