Applications Home Page
Radiation Antidote for Defense
Despite the significant threat of high dose radiation exposure that exists in our world today, there are currently no highly effective and non-toxic anti-radiation treatments available. CBLI is building upon its understanding of the molecular mechanisms by which radiation induces cell death to develop pharmaceuticals that address this need. CBLI’s Protectan compounds rescue mammals from lethal doses of radiation by suppressing apoptotic cell death in critical hematopoietic (HP) and/or gastrointestinal (GI) tract cells. The effectiveness of Protectans whether injected before or after radiation exposure indicates that these compounds have great potential as practical, as well as effective and non-toxic, biodefense measures.
Background and Rationale
With rogue nations developing nuclear capabilities and almost 30,000 nuclear warheads deployed around the world, the possibility of nuclear warfare is an unfortunate reality. In addition, the risk of a terrorist attack involving either a nuclear weapon, a “dirty bomb” (a combination of conventional explosives and nuclear material), or an attack on a nuclear power plant or waste site is a top concern for many countries. The possibility of an accident at a nuclear power plant (104 in the U.S. and 439 worldwide) presents another potentially daunting source of radiation. A Nuclear Regulatory Commission study stated that breaching a cask of spent fuel could release lethal radiation over an area many times larger than that affected by a 10 kiloton nuclear weapon.
The need for countermeasures against these threats is dire since there are currently no pharmaceuticals approved for use in protecting humans from acute radiation injury. The only agent that has been widely stockpiled to date for use in the event of an act of nuclear terrorism or a nuclear accident is potassium iodide (KI). However, KI is only effective against the long-term risk of cancer developing ten to fifteen years post-exposure. It does not protect the body from the acute effects of high dose radiation that can lead to death within days or weeks.
The short term lethality of high dose ionizing radiation is due to development of Acute Radiation Syndrome (ARS) caused by massive apoptosis in radiosensitive organs, including the hematopoietic (HP) system and the gastrointestinal (GI) tract. Other cell types, such as spermatocytes and hair follicles, are also affected. HP and GI acute radiation syndromes are induced by different levels of radiation and have highly predictable clinical courses. In humans, whole-body or significant partial body exposure to less than 3.5 Gy results in only moderate bone marrow (HP) damage and survival is probable. However, survivors are likely to suffer from severe immunosuppression and/or an increased risk of cancer. Exposure to 3.5-7.5 Gy induces severe bone marrow damage and death is probable within 2-6 weeks. Significant GI damage occurs in addition to HP damage at doses over 5 Gy, and at doses over 7.5 Gy, death typically occurs within 1-2 weeks. At doses of 10 Gy and higher, cerebrovascular dysfunction becomes a leading factor in death within days. It is estimated that nearly all survivors of the 1945 blast at Hiroshima received doses of less than 3 Gy. Chernobyl firefighters were likely exposed to 6-7 Gy.
CBLI’s unique approach of pharmacological modulation of apoptosis is ideally suited to address the need for effective radiation countermeasures. The company is currently developing derivatives of microbial factors that are natural regulators of apoptosis as Protectans, molecules that prevent death of normal cells in the face of stresses such as radiation. As described below, the lead Protectan compounds CBLB502 and CBLB600 series have significant activity as both radioprotectants (injected prior to radiation exposure) and mitigators of radiation damage (injected after radiation exposure). The underlying principle of radioprotection by Protectans and their structures and uses represent the intellectual property of CBLI developed in collaboration with the Cleveland Clinic.
Lead Compounds
Protectan CBLB502
Protectan CBLB502 is a rationally designed recombinant derivative of the bacterial protein, flagellin, which binds and activates the mammalian TLR5 cell surface receptor. CBLI initially chose to explore flagellin as a potential radioprotectant since its signaling through TLR5 is known to activate the anti-apoptotic NF-kappaB pathway. Moreover, TLR5 is expressed on the endothelial cells of the small intestine lamina propria, the most radiosensitive part of the GI tract.
Extensive preclinical studies have demonstrated that CBLB502 is an effective and non-toxic anti-radiation treatment. The compound rescues both mice and non-human primates (Macaca mulatta) from lethal doses of total body gamma radiation, whether injected prior to, or after, radiation exposure. CBLB502 is non-toxic at therapeutic doses in both mice and monkeys. Importantly, CBLB502 protects cells of both the HP system and the GI tract. GI protection is a unique advantage of CBLB502 over any currently known radioprotectant or radiomitigator. CBLB502 is highly stable and is effective when administered through intramuscular injection, characteristics important for practical application as an emergency or military field treatment.
CBLB502 Development Status: CBLI plans to initiate clinical studies of CBLB502 as a radioprotectant for medical applications, such as Supportive Care in Cancer Treatment in 2009. However, since CBLB502 also presents a highly promising approach to biodefensive radioprotection, CBLI is currently focused on expedited development of the drug for “non-medical” biodefense applications. The “Animal Efficacy“ rule developed by the U.S. Food and Drug Administration (FDA) in 2002 eliminates the requirement for Phase II and Phase III clinical trials for investigational drugs that address situations such as radiation injury, since it would be infeasible and/or unethical to conduct efficacy studies in humans. In such cases, drugs are considered for approval based upon only Phase I safety studies in humans and efficacy studies in two animal species. Development of CBLB502 under this rule has been supported in part by more than $25 million in contracts from the Department of Defense (DoD) and the Biomedical Advanced Research and Development Authority (BARDA) of the Department of Health and Human Services (HHS), as well as other federal agencies. CBLI expects to submit a BLA for FDA approval in late 2010. Animal efficacy studies, and cGMP manufacturing have been completed. Human safety studies are currently ongoing, as is investigation of the drug’s extended stability, final formulation and delivery devices.
View Product Pipeline
CBLB600 Series Protectans
In addition to CBLB502, CBLI initially investigated the radioprotective potential of a series (CBLB600 Series Protectans) of pharmacologically improved synthetic derivatives of mycoplasma lipopeptide. Mycoplasma lipopeptide is the natural agonist of heterodimeric TLR2/TLR6 receptors expressed on mammalian cells. Signaling through this receptor results in activation of the anti-apoptotic NF-kappaB pathway.
Preclinical investigation of CBLB600 Series compounds as radioprotectants has demonstrated that they protect mice and non-human primates from death due to HP acute radiation syndrome when administered either before or after radiation exposure. The compounds are non-toxic at therapeutic doses in mice, are highly stable, and can be effectively delivered by intramuscular or subcutaneous injection. A striking feature of CBLB600 Series Protectans is that, in the absence of irradiation, their administration stimulates proliferation of bone marrow hematopoietic stem cells and induces their migration to the peripheral blood. Given the advanced nature of Protectan CBLB502’s development as an antidote for radiation exposure, CBLI has redirected the clinical development of the CBLB600 Series Protectans to other potential medical applications, such as Stem Cell Induction and Mobilization in the context of recovery from chemotherapy-induced myelosuppression, or bone marrow transplant.
View Product Pipeline
Supportive Care in Cancer Treatment
The side effects that accompany cancer treatments involving ionizing radiation or chemotherapy present significant health issues and limit the dose (and therefore effectiveness) of the treatment. These side effects are largely determined by stress-induced apoptotic death of normal cells in sensitive tissues. CBLI’s Protectan compounds specifically inhibit this process, while not affecting therapy-induced killing of tumor cells. Thus, these compounds have strong potential to play a major role in medical applications as an adjuvant to cancer therapy.
Given the prevalence of cancer (approximately 1.4 million new cases each year in the U.S. alone) and the fact that more than 70% of patients are impacted by treatment side effects, there is a significant global market for drugs that limit side effects and, therefore, allow more intense and effective treatment regimens. Cancer treatment side effects largely result from stress-induced apoptosis of normal cells in sensitive tissues. This includes intestinal cells (leading to nausea), hair follicles (leading to hair loss), spermatocytes (leading to male infertility) and hematopoietic (HP) cells (leading to immunosuppression).
The factor that typically determines the dose limits for radiation therapy is the onset of gastrointestinal (GI) syndrome (abdominal pain, nausea, diarrhea, vomiting accompanied by systemic effects such as malabsorption, dehydration, bowel obstruction, anemia, bleeding, sepsis, etc.) due to loss of the epithelial cells lining the GI tract. Pharmacological protection of these cells would allow for increased radiation doses to more effectively eliminate tumor cells. This, of course, requires that the drug does not also act as a radioprotectant in tumor cells.
CLBI’s Protectans technology presents an ideal strategy for counteracting cancer treatment side effects. While normal “bystander” tissues are damaged by cancer treatments through apoptotic cell loss, most tumors have defects in their apoptotic machinery and are killed through non-apoptotic mechanisms. Thus, Protectans that are designed to imitate survival mechanisms developed by tumor cells – suppression of apoptosis via inhibition of p53 and/or activation of NF-kappaB – would be expected to protect normal, but not tumor, cells.
Indeed, CBLI has shown both in vitro and in vivo that its lead Protectan, CBLB502, protects normal cells of both the GI and HP systems from radiation-induced cell death, yet has no effect on the radiosensitivity of a diverse set of tumor cell types. For example, in mouse models, tumors can be eliminated by radiation treatment; however, this “therapeutic effect” is accompanied by death due to radiation toxicity. Treatment with CBLB502 together with radiation allows the mice to survive while tumor cells are eliminated. CBLB502 is an optimized derivative of bacterial flagellin that signals through the TLR5 cell surface receptor to activate the anti-apoptotic NF-kappaB pathway.
Radioprotective doses of CBLB502 are non-toxic and non-carcinogenic. The compound provides long-term radioprotection with no development of delayed-onset radiation-induced sickness. Moreover, CBLI has demonstrated that the drug is effective against multiple fractionated doses of radiation mimicking typical cancer therapy regimens and that repeated administration of CBLB502 does not diminish its activity.
CBLI has also conducted animal studies demonstrating CBLB502’s ability to reduce the side effects of a chemotherapeutic drug, cisplatinum (Ciplatin, Platinol) broadly used for treatment of ovarian, endometrial, head and neck, lung, stomach and other types of cancer.
CBLI intends to initiate a Phase I/II clinical study of CBLB502 for the reduction of occurrence and severity of a common condition known as mucositis in head and neck cancer patients receiving both radiation and chemotherapy in the Spring of 2009.
View Product Pipeline
Acute Organ Failure
CBLI’s finding that Protectans are able to prevent death of normal cells in the face of stresses that normally induce apoptosis suggests a wide range of potential applications for these compounds. In addition to radiation exposure, another type of stress that leads to tissue damage through apoptosis of normal, non-cancerous cells is the ischemia (limited blood flow leading to local hypoxia) that occurs during acute medical conditions such as stroke, heart attack and renal failure.
CBLI researchers in collaboration with investigators from the Cleveland Clinic have demonstrated that injection of Protectan CBLB502, an optimized derivative of bacterial flagellin, effectively prevents acute renal failure and subsequent death in a mouse model of ischemia-reperfusion renal injury. Thus, CBLI expects that this class of drugs will be useful in limiting the tissue damage associated with a number of different acute organ failure scenarios. Pre-clinical studies aimed at validating this hypothesis are ongoing.
The anti-ischemia effect of CBLB502 also has a potentially important defense application. The compound is being tested for its ability to reduce tissue damage associated with the use of tourniquets to prevent excessive bleeding from wounded limbs. If effective in this scenario, CBLB502 could allow significantly broader use of tourniquets, which has been limited by the high risk of limb loss due to prolonged tissue hypoxia. Systemic and local effects of tourniquet use are described in http://www.jbjs.org.uk/cgi/reprint/62-B/3/385.pdf.
Stem Cell Induction and Mobilization
A unique property of the CBLB600 series of Protectans is that injection of these compounds results in increased numbers of hematopoietic stem cells (HSC) in both the bone marrow and peripheral blood. This activity may contribute to the radioprotective effects of CBLB600 Series compounds. Moreover, given the ability of HSC to self-renew and differentiate into all of the different types of blood and immune cells and potentially other cell types as well, these findings present innovative options for treatment of a broad spectrum of human diseases, some of which currently lack effective treatment.
The differentiated cells that constitute our organs, including the hematopoietic (HP) system, originate from a pluripotent population of stem cells. While most differentiation occurs during embryonic development, a small number of “adult stem cells” persist in various tissues of the body throughout adulthood serving to replace cells that are lost due to injury, disease or normal attrition. The best studied population of adult stem cells is the HSCs that reside in the bone marrow, with a small fraction circulating in the peripheral blood. HSCs undergo cell division resulting in self-renewal of the HSC population as well as progeny HSCs that can differentiate into all of the different types of blood cells. In addition, there is evidence suggesting that bone marrow HSCs may undergo “transdifferentiation” to form other, non-blood cell types, including skeletal and cardiac muscle cells, brain cells, liver cells, skin cells, lung cells, kidney cells, intestinal cells, and pancreatic cells. The great potential for medicinal use of stem cells lies in the theoretical possibility that, given the right conditions, stem cells can be manipulated to generate any desired cell type. This would allow damaged organs or tissues to be replaced with an exact genetic match arising from stems cells from the individual patient, eliminating the need for donors and immunosuppression and the risk of transplant rejection.
Transplantation of bone marrow-derived HSC has been used clinically since 1959 in the form of total bone marrow transplantation to treat hematopoietic cancers (leukemias and lymphomas) and to aid immune system recovery from high-dose chemotherapy of non-hematopoietic cancers. Other indications for HSC use include diseases that involve genetic or acquired bone marrow failure, such as aplastic anemia, thalassemia, sickle cell anemia, and autoimmune diseases. In addition to these traditional uses, stem cells are also being investigated as potential treatments for diseases such as diabetes, heart disease, Parkinson’s disease, etc. where the primary defect is not necessarily in a blood cell compartment.
An important advance in the clinical use of HSCs came from the finding that the small number of HSCs circulating in the peripheral blood can be increased by injecting the donor with the purified cytokine, granulocyte-colony stimulating factor (G-CSF). Recombinant forms of G-CSF (Neupogen® and Neulasta®) are among the lead products of Amgen, bringing in revenues of approximately $4.5 billion through their use in treatment of a broad range of clinical conditions requiring restoration of the immune system. Mobilization of HSCs to the circulation via G-CSF treatment allows them to be collected for transplantation in a much less invasive procedure from the peripheral blood rather than the bone marrow. As described below, CBLB600 Series Protectans represent a new, and perhaps improved, class of drugs for this application.
CBLI’s lead compound for stem cell applications is Protectan CBLB612, a pharmacologically improved synthetic derivative of mycoplasma lipopeptide. Like native mycoplasma lipopeptide, CBLB612 and other CBLB600 Series Protectans bind and activate the mammalian TLR2/TLR6 heterodimeric cell surface receptor, resulting in activation of NF-kappaB and inhibition of stress-induced apoptosis in normal cells. This activity contributes to protection of the HP system and increased survival of mice following exposure to lethal doses of radiation (LINK: see Radiation Antidote for Defense application page). In examining the radioprotective effect of CBLB600 Series compounds, CBLI found that circulating G-CSF levels were increased following administration of the compounds. Given the known stimulatory effect of G-CSF on HSCs, these data suggest that 1) upregulation of G-CSF might play a role in the radioprotective efficacy of CBLB600 Series Protectans, and 2) CBLB600 Series compounds might be useful in other medical applications through induction of HSC. Indeed, CBLI found that a single administration of CBLB612 (in the absence of radiation) resulted in powerful induction of HSCs in both mice and non-human primates (Macaca mulatta). Increased numbers of HSC were found in both the bone marrow and the peripheral blood. Circulating HSCs induced by CBLB612 in mice were fully functional in that transferred peripheral blood was capable of rescuing lethally irradiated mice from bone marrow deficiency.
These data demonstrate that CBLB600 Series Protectans may be useful drugs for medical applications that require harvesting of HSCs. These Protectans are as efficient as G-CSF in inducing bone marrow HSCs and mobilizing them to enter the circulation, yet only require a single injection and are more cost effective. Moreover, there is opportunity for use of CBLB600 Series Protectans in combination with G-CSF or as a substitute in G-CSF-insensitive patients.
CBLI is currently engaged in additional preclinical studies focused on specific aspects of the activity of CBLB612 on stem cells. These studies include investigation of the effect of the compound on 1) recovery from the myelosuppression (reduced bone marrow activity) that accompanies chemotherapy, 2) restoration of the vasculature in injured tissues/healing wounds, and 3) collection of HSCs from peripheral blood by stem cell apharesis, the procedure currently used to generate an enriched pool of stem cells that can be stored and used in place of bone marrow.
Development of CBLB600 Series Protectans for stem cell applications will benefit from the accelerated development on the compounds as Radiation Antidotes for Defense that is currently underway.
View Product Pipeline
Cancer Treatment
One of the major applications of CBLI’s apoptosis-modulating technology is for cancer treatment. Most human tumors acquire defects that make them resistant to apoptosis such as constitutive activation of the anti-apoptotic factor NF-kappaB and /or inactivation of the pro-apoptotic factor p53. Pharmacological restoration of apoptotic pathways could result in direct tumor cell killing or sensitization of tumor cells to the effects of traditional cancer therapies. CBLI has discovered several classes of proprietary small molecule compounds, called Curaxins, that simultaneously inactivate NF-kappaB signaling and restore p53 signaling, effectively reversing the death-resistant tumor phenotype. Given the significant incidence of cancer worldwide and the lack of effective treatments for many types of malignant disease, Curaxins have the potential to make an important impact on a large oncology market.
Background and Rationale
The initial focus of CBLI’s anti-cancer drug development program was one of the most treatment-resistant types of cancer, a highly fatal form of kidney cancer called renal cell carcinoma (RCC). A drug discovery program was initiated to identify small molecules that selectively destroy tumor cells by restoring normal activity to the wild type, but functionally impaired, p53 expressed in RCC. This program yielded a number of molecules with the desired properties, which were named Curaxins.
Curaxins have a unique mechanism of action that involves simultaneous activation of p53 and inhibition of NF-kappaB, thus reversing two of the conditions frequently associated with tumor onset and maintenance. Strategies targeting p53 or NF-kappaB independently have been validated as cancer therapies; however, Curaxins are the only compounds currently known to CBLI that simultaneously target both pathways.
Since NF-kappaB induces expression of numerous genes with anti-apoptotic, cell growth-inducing and pro-inflammatory functions, the constitutive NF-kappaB activity typical of tumor cells renders them resistant to apoptosis and supports tumor cell proliferation, motility, metastasis and angiogenesis. Importantly, Curaxins inhibit the function of both basal and activated NF-kappaB by “reprogramming” NF-kappaB-containing protein complexes from transcription activators to transcription repressors. Thus, Curaxins are most effective in tumor cells since they contain increased levels of total NF-kappaB protein as compared to normal cells. This suggests that Curaxins might be useful in sensitizing tumor cells to traditional therapies that otherwise impair their own anti-cancer activity by inducing NF-kappaB.
The p53 tumor suppressor gene is frequently mutated or deleted in human cancers. Moreover, p53 is functionally compromised in about 50% of tumors that retain the wild type p53 gene. Curaxins restore functionality to the wild type p53 protein in such tumor cells. Importantly, unlike traditional chemotherapeutic agents, activation of p53 by Curaxins does not involve induction of DNA damage.
Discovery of the mechanism of action of Curaxins allowed CBLI to predict and later experimentally verify that Curaxins could be used for treatment of multiple forms of cancers, including RCC, hormone-refractory prostate cancer, hepatocellular carcinoma, multiple myeloma, acute lymphocytic leukemia, acute myeloid leukemia, soft-tissue sarcoma and others.
While Curaxins are most effective in inducing death of tumor cells retaining wild type p53, they also display significant toxicity towards p53-deficient tumor cells, suggesting that inactivation of NF-kappaB on its own can be sufficient to achieve the desired therapeutic effect. This greatly broadens the potential use of Curaxins in patients regardless of the p53 status of their tumor.
CBLI’s lead product candidate for cancer treatment is Curaxin CBL102, which is currently in Phase II clinical trials. Other Curaxins are being validated in preclinical studies.
Lead Compounds
Curaxin CBLC102
One of CBLI’s first generation Curaxins with a 9-aminoacridine-related structure (CBLC102) is the well-known compound Quinacrine. Quinacrine has been used in humans for over 60 years to treat malaria, osteoarthritis, autoimmune disorders and other conditions. However, its ability to destroy tumors through inactivation of NF-kappaB signaling and restoration of p53 signaling is a novel discovery made by CBLI.
CBLI’s development of Quinacrine for the novel application of cancer treatment has benefited from its long history of human use. The compound has well-established toxicity and pharmacokinetics profiles and is characterized as a safe, non-carcinogenic and orally available drug.
CBLI has demonstrated that CBLC102 (Quinacrine) displays significant cytotoxic activity against human malignant cell lines of multiple origins, including renal cell, prostate, colon, lung, and hepatocellular carcinoma, sarcoma, multiple myeloma and leukemia. At the same time, CBLC102 shows minimal in vitro cytotoxicity towards prototype normal cells. While CBLC102 is most potent against tumor cells expressing wild type p53, the compound also displays significant toxicity against p53-negative cancers. Notably, cell lines that are resistant to standard chemotherapy (for example, doxorubicin) were found to be sensitive to CBLC102. In vivo experiments using human tumor xenografts in mice confirmed the anti-cancer activity of CBLC102.
Development Status of CBLC102:
Due to established safety in humans through its prior use, CBLC102 was eligible for expedited development (fast track to Phase II) as a novel anti-cancer agent with a unique mechanism of action. CBLI has an agreement with Regis Technologies, Inc., a cGMP manufacturer, to produce CBLC102 according to the established process used when the drug was in common use. CBLI launched a Phase II study with CBLC102 in January 2007 to provide proof of safety and of anti-neoplastic activity in cancer patients and establish a foundation for clinical trials of CBLI’s new proprietary Curaxin molecules, which have been designed and optimized for maximum anticancer effects, as well as for additional treatment regimens based on ongoing research into the precise molecular mechanisms of action of Curaxins.
Thirty-one patients were enrolled in a Phase II study of CBLC102 as a monotherapy in late stage, hormone-refractory taxane-resistant prostate cancer. All patients had previously received hormonal treatment for advanced prostate cancer and 28 of the 31 had also previously received chemotherapy. One patient had a partial response, while 50% of the patients exhibited a decrease or stabilization in PSA velocity, a measure of the speed of prostate cancer progression. CBLC102 was well tolerated and there were no serious adverse events attributed to the drug.
This clinical evidence indicates several opportunities for extending development of CBLC102 into other cancer types, dose escalation or use in combination with existing therapies. The Company will be evaluating these opportunities, while moving more aggressively forward with a new generation of more powerful, proprietary Curaxin molecules with similar mechanisms of action, which offer improved patent protection.
Next Generation Curaxins
CBLI has successfully completed a comprehensive hit-to-lead optimization program directed towards development of new proprietary Curaxin molecules simultaneously targeting p53 and NF-kB. Working in partnership with ChemBridge Corporation, a chemical libraries manufacturer and CBLI co-founder, the Company has developed CBLC137; which is a drug candidate with proprietary composition of matter intellectual property protection belonging to CBLI’s next generation of highly improved Curaxins.
CBLC137 has demonstrated reliable anti-tumor effects in animal models of colon, breast, renal and prostate cancers. CBLC137 has favorable pharmacological characteristics, is suitable for oral administration and demonstrates a complete lack of genotoxicity. It shares all of the positive aspects of CBLC102, but significantly exceeds the former compound’s activity and efficacy in preclinical tumor models. CBLC137 is currently undergoing manufacturing and preclinical toxicology studies in preparation for clinic trials in early 2010.
Development Status of Next generation Curaxins: CBLC137 is currently undergoing manufacturing and preclinical toxicology studies in preparation for clinic trials in early 2010.
View Product Pipeline
| 
