Developing Novel Drugs for Treatment and Diagnosis of Cancer

CLR1404 (COLD)

COLD is a cancer-targeted chemotherapy that, in pre-clinical experiments, inhibits the phosphatidylinosotol 3-kinase (PI3K)/Akt survival pathway, which is overexpressed in many types of cancer. We believe COLD has the potential to be best-in-class versus other Akt inhibitors in development. We believe that COLD has important advantages over competitor agents including:

Selective uptake and retention by cancer cells/cancer stem cells compared to normal cells/stem cells. This results in significantly greater potency of COLD as an inhibitor of cell proliferation in cancer cells vs. normal cells (greater than a 10-fold difference), or
Suitability for intravenous administration, avoiding dose-limiting gastrointestinal toxicity seen with orally administered Akt-inhibiting APCs and potentially enabling greater systemic drug exposure and, hence, Akt-inhibition in cancer cells, resulting in superior efficacy.

Chemically, COLD is 18-(p-[¹²⁷I] iodophenyl) octadecyl phosphocholine, an alkyl phosphocholine (APC) subtype within the phospholipid ether (PLE) class. The iodine atom in its structure is the stable, non-radioactive (“cold”) isotope, ¹²⁷I.

COLD exhibits significant in vivo efficacy in mouse xenograft tumor models, including non-small cell lung cancer and triple-negative breast cancers. In these models, human cancer cells are transplanted to and grow/metastasize in immunosuppressed animals. Tumor-bearing mice treated therapeutically (i.e., after primary tumors were established) with COLD i.v. (100-times the mass dose used as a carrier in the radiotherapy agent, HOT) once a week for 5 weeks, showed almost complete suppression of tumor growth compared to saline-treated control animals. Tumor growth suppression by COLD was maintained long after the end of the treatment period. Importantly, survival in COLD-treated groups at experiment termination (100-200 days post tumor-cell injection) was 90% or more compared to 20% or less in control groups. Additionally, in a side-by-side comparison, COLD was much more effective in suppressing tumor growth and increasing survival in the lung cancer model than a standard dosing regimen of erlotinib (Tarceva, a marketed epidermal growth factor receptor kinase inhibitor).

The in vivo efficacy of COLD is believed to be at least in part the result of selective inhibition of the apoptosis-suppressing PI3K/Akt signaling pathway in cancer cells. This pathway, which is activated by growth factors such as PDGF (platelet-derived growth factor), EGF (epidermal growth factor), and insulin, is overactive in many human cancers and contributes to cell growth, proliferation, survival and resistance to radiation and chemotherapeutics. COLD selectively inhibits Akt activation in human cancer cells compared to normal proliferating cells (e.g., human fibroblasts). At the same concentrations, COLD induces caspase-mediated apoptosis and suppresses proliferation in a wide range of human cancer cell lines including prostate carcinoma, ovarian carcinoma, triple-negative breast carcinomas, pancreatic adenocarcinoma and non-small cell lung cancer. At these concentrations, COLD does not inhibit proliferation of normal cells.

Other cancer targeting APCs have also been reported to be active in xenograft models and to selectively inhibit tumor cell proliferation via a mechanism that involves induction of caspase-mediated apoptosis subsequent to inhibition of Akt activation and signaling. However, APCs are generally dose-limited in vivo (including in man) by side effects stemming from the necessity for their oral administration (due to their hemolytic properties), thus limiting Akt inhibition and anti-tumor efficacy. In contrast, data to date support the contention that COLD can be safely administered intravenously at doses that we believe will result in greater drug exposure compared to other APCs and, thus, in greater Akt inhibition and improved efficacy.

Non-APC Akt inhibitors in development are not cancer-targeting and thus have the potential for an unfavorable therapeutic index (due to non-selective inhibition of Akt, and hence proliferation) in normal vs. cancer cells. In contrast, selective uptake and retention of COLD results in more than 10-fold more potent inhibition of Akt activity and cell proliferation in cancer cells vs. normal cells.