Calando Pharmaceuticals is creating and developing new targeted, siRNA-containing therapeutics using its proprietary RONDEL™ technology. Calando combines proprietary technologies in targeted polymeric delivery systems and to create effective therapeutics. The company is pursuing this goal through both its internal R&D group and collaborations and partnerships with pharmaceutical and biotechnology companies.

CALANDO’S RONDEL™ TECHNOLOGY

Calando’s cyclodextrin-containing polymers form the foundation for its three-part RNAi/Oligonucleotide Nanoparticle Delivery (RONDEL™) technology. The first component is a linear, cyclodextrin-containing polycation that, when mixed with small interfering RNA (siRNA) binds to the anionic “backbone” of the siRNA. The polymer and siRNA self-assemble into nanoparticles less than approximately 100 nm diameter that fully protect the siRNA from nuclease degradation in serum.  The cyclodextrin in the polymer enables the surface of the particles to be decorated by stabilizing agents and targeting ligands. These surface modifications are formed by proprietary methods involving the cyclodextrins.

The surface-modifying agents have terminal adamantane groups that form inclusion complexes with the cyclodextrin and contain poly(ethylene glycol) (PEG) to endow the particles with properties that prevent aggregation, enhance stability and enable systemic administration.  Ligands to cell surface receptors can be covalently attached to the adamantane-PEG modifier, enabling the siRNA-containing particles to be targeted to tissues of interest.

The siRNA delivery system has been designed for intravenous injection. Upon delivery to the target cell, the targeting ligand binds to membrane receptors on the cell surface and the RNA-containing nanoparticle is taken into the cell by endocytosis. There, chemistry built into the polymer functions to unpackage the siRNA from the delivery vehicle.

ADVANTAGES OF CALANDO'S RONDEL™ TECHNOLOGY

Calando’s RONDEL™ technology offers the following advantages:  

Generalized delivery systems – Binds to and self-assembles with the siRNA to form uniform colloidal-sized particles. Analysis has shown that these particles are spherical and less than approximately 100 nm in diameter.

Stealthy to the immune system – The delivery vector allows for repeat dosing without the risk of immune reactions. Unlike lipid delivery vehicles, the cyclodextrin-based RONDEL™ delivery system does not cause an interferon response.

Safety – Has been shown to be non-toxic in in vitro testing with human cell cultures, and the fully formulated polymer/siRNA particles exhibits a significant therapeutic window of safety in animals, even when repeated doses (up to 8 doses over a four week period) are used.

Stable under physiological conditions – Particles have been shown to be stable under physiological conditions. 

Efficient in targeted delivery – Calando and its partners have demonstrated successful delivery of functional siRNA therapeutics to tumor cells and to hepatocytes by systemic administration and confirmed sequence-specific gene inhibition.

Fully integrated system – Calando has made significant advances in the design and development of non-viral delivery systems that overcome the extra- and intra-cellular barriers to siRNA delivery. The company is the only one to integrate both siRNA technology with delivery technology to create an effective siRNA therapeutic. 

 EXEMPLARY RESULTS

Calando and its collaborators have generated preclinical data that demonstrate sequence-specific inhibition of tumors from the systemic administration of targeted formulations of siRNA.

Using the RONDEL™ delivery system and siRNA developed at Calando targeting the M2 subunit of ribonucleotide reductase (RRM2), in collaboration with colleagues at the Livingston Research Institute, reduced tumor growth rates and/or tumor reduction have been observed in a variety of animal cancer models.  Results for murine hepatoma (Hepa1-6) and human melanoma (HT144) tumors are shown below.

[Treatments were made using female C57BL/6 mice containing subcutaneous Hepa1-6 (murine hepatoma) tumors.  All doses refer to the amount of the siRNA component within the Tf-targeted RONDEL™ delivery system.  Doses were administered via normal-pressure tail vein injection on Days 1, 3, 8, and 10 (except for formulated siCONTROL, which was administered on Days 1 and 8 only).  CALAA-01 refers to siRNA against the M2 subunit of ribonucleotide reductase (RRM2) formulated within the RONDEL™ delivery system.  Tumor volume was calculated from caliper measurement of tumor dimensions.  Each treatment group contained n=5 mice.]

[Treatments were made using female athymic nude mice containing subcutaneous HT144 (human melanoma) tumors.  All doses refer to the amount of the siRNA component within the Tf-targeted RONDEL™ delivery system.  Doses were administered via normal-pressure tail vein injection on Days 1, 3, 8, 10, 22, 24, 29, and 31 (except for formulated siCONTROL, which was administered on Days 1, 3, 8, and 10 only).  CALAA-01 refers to siRNA against the M2 subunit of ribonucleotide reductase (RRM2) formulated within the RONDEL™ delivery system.  Tumor volume was calculated from caliper measurement of tumor dimensions.  Each treatment group contained n=5 mice.]

In addition, workers at Caltech and Children’s Hospital-Los Angeles used nanoparticles made with the RONDEL™ delivery system and siRNA against the EWS-Fli1 fusion gene to prevent tumor growth in a disseminated murine model of Ewing’s sarcoma.

[Treatments were made using female NOD/SCID mice injected with luciferase-expressing TC71 (human Ewing’s sarcoma) cells.  All doses were 2.5 mg/kg, with respect the siRNA component.  Doses were administered twice-weekly for four weeks.  Arrows indicate days of dosing.  Each treatment group contained n=10 mice.]

In addition, numerous safety evaluations have been completed or are ongoing, as well as additional efficacy studies in animal models.  Please refer to our list of publications for more information.