Current approaches in enhancing TRAIL therapies in glioblastoma

Glioblastoma (GBM) is the most prevalent, aggressive, primary brain cancer in adults and continues to pose major medical challenges due in part to its high rate of recurrence. Extensive research is underway to discover new therapies that target GBM cells and prevent the inevitable recurrence in patients. The pro-apoptotic protein tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) has attracted attention as an ideal anticancer agent due to its ability to selectively kill cancer cells with minimal toxicity in normal cells. Although initial clinical evaluations of TRAIL therapies in several cancers were promising, later stages of clinical trial results indicated that TRAIL and TRAIL-based therapies failed to demonstrate robust efficacies due to poor pharmacokinetics, resulting in insufficient concentrations of TRAIL at the therapeutic site. However, recent studies have developed novel ways to prolong TRAIL bioavailability at the tumor site and efficiently deliver TRAIL and TRAIL-based therapies using cellular and nanoparticle vehicles as drug loading cargos. Additionally, novel techniques have been developed to address monotherapy resistance, including modulating biomarkers associated with TRAIL resistance in GBM cells. This review highlights the promising work to overcome the challenges of TRAIL-based therapies with the aim to facilitate improved TRAIL efficacy against GBM.

Antibody conjugated nanoparticles as a novel form of antibody drug conjugate chemotherapy

Antibody conjugated nanoparticles (ACNPs) represent a novel strategy for the development of therapies exploiting antibodies to augment the delivery of chemotherapy payloads. Following in the footsteps of the success of antibody drug conjugates (ADCs), ACNPs are only now reaching clinical evaluation. In this review we discuss the success of ADCs and explore the opportunities ACNPs offer, such as broad chemotherapy payload selection, high drug to antibody ratios and the ability to finely tailor drug release in comparison to ADCs. The ability of ACNPs to elicit increased avidity due to multivalent effects and the potential to use these modular platforms in immunotherapeutic approaches is also explored. Through addressing challenges that still remain in bringing these complex formulations to the clinic, ACNPs hold obvious potential for the treatment of a wide range of cancers and other diseases where selective targeting of drug agents is essential.

Apo2L/TRAIL and the death receptor 5 agonist antibody AMG 655 cooperate to promote receptor clustering and antitumor activity

Death receptor agonist therapies have exhibited limited clinical benefit to date. Investigations into why Apo2L/TRAIL and AMG 655 preclinical data were not predictive of clinical response revealed that coadministration of Apo2L/TRAIL with AMG 655 leads to increased antitumor activity in vitro and in vivo. The combination of Apo2L/TRAIL and AMG 655 results in enhanced signaling and can sensitize Apo2L/TRAIL-resistant cells. Structure determination of the Apo2L/TRAIL-DR5-AMG 655 ternary complex illustrates how higher order clustering of DR5 is achieved when both agents are combined. Enhanced agonism generated by combining Apo2L/TRAIL and AMG 655 provides insight into the limited efficacy observed in previous clinical trials and suggests testable hypotheses to reconsider death receptor agonism as a therapeutic strategy.

Anticancer activity of the type I insulin-like growth factor receptor antagonist, ganitumab, in combination with the death receptor 5 agonist, conatumumab

Agents targeting the insulin-like growth factor receptor type 1 (IGF1R) have shown antitumor activity. Based on the evidence for interaction between the IGF-1 and TRAIL pathways, we hypothesized that the combination of ganitumab (monoclonal antibody to IGF1R) with the pro-apoptotic death receptor 5 agonist, conatumumab, might increase antitumor response. Ganitumab and conatumumab were tested in combination in a Colo-205 xenograft model. Part 1 of the clinical study was a phase Ib program of three doses of conatumumab (1, 3, 15 mg/kg) in combination with 18 mg/kg ganitumab to determine the maximum tolerated dose (MTD) in patients with advanced solid tumors. Part 2 was conducted in six cohorts with advanced non-small cell lung cancer (squamous or non-squamous histology), colorectal cancer, sarcoma, pancreatic cancer, or ovarian cancer, treated at the recommended doses of the combination. The combination was significantly more active in the Colo-205 xenograft model than either single agent alone (p < 0.0015). In part 1 of the clinical study, no dose-limiting toxicities were observed and the MTD of conatumumab was 15 mg/kg in combination with 18 mg/kg ganitumab. In part 2, 78 patients were treated and there were no objective responses but 28 patients (36 %) had stable disease (median 46 days, range 0-261). The combination was well-tolerated with no new toxicities. In conclusion, the combination of ganitumab and conatumumab was well-tolerated but had no objective responses in the population tested. The successful future application of this combination of antitumor mechanisms may rely on the identification of predictive biomarkers.

Death receptor agonist therapies for cancer, which is the right TRAIL?

The activation of cell-surface death receptors represents an attractive therapeutic strategy to promote apoptosis of tumor cells. Several investigational therapeutics that target this extrinsic pathway, including recombinant human Apo2L/TRAIL and monoclonal agonist antibodies directed against death receptors-4 (DR4) or -5 (DR5), have been evaluated in the clinic. Although Phase 1/1b studies provided encouraging preliminary results, findings from randomized Phase 2 studies failed to demonstrate significant clinical benefit. This has raised multiple questions as to why pre-clinical data were not predictive of clinical response. Results from clinical studies and insight into why current agents have failed to yield robust responses are discussed. In addition, new strategies for the development of next generation death receptor agonists are reviewed.

TRAIL receptor agonist conatumumab with modified FOLFOX6 plus bevacizumab for first-line treatment of metastatic colorectal cancer: A randomized phase 1b/2 trial

BACKGROUND

In patients with previously untreated metastatic colorectal cancer (mCRC), we conducted a phase 1b/randomized phase 2 trial to define the safety, tolerability, and efficacy of mFOLFOX6 plus bevacizumab (mFOLFOX6/bev) with conatumumab, an investigational, fully human monoclonal IgG1 antibody that specifically activates death receptor 5 (DR5).

METHODS

Twelve patients were enrolled in a phase 1b open-label dose-escalation trial of conatumumab with mFOLFOX6/bev; thereafter, 190 patients were randomized 1:1:1 to receive mFOLFOX6/bev in combination with 2 mg/kg conatumumab, 10 mg/kg conatumumab, or placebo. Therapy cycles were repeated every 2 weeks until disease progression or the occurrence of unacceptable toxicity.

RESULTS

In phase 1b, conatumumab with mFOLFOX6/bev was tolerated without apparent added toxicity over mFOLFOX6/bev alone. In phase 2, conatumumab with mFOLFOX6/bev did not confer a benefit in progression-free survival when compared with placebo with mFOLFOX6/bev. Toxicity was similar in all treatment arms. Following treatment, similar increases in circulating caspase-3 levels were observed in all arms.

CONCLUSIONS

Conatumumab with mFOLFOX6/bev did not offer improved efficacy over the same chemotherapy with placebo in first-line treatment of patients with mCRC. These data do not support further development of conatumumab in advanced CRC.

A randomized, placebo-controlled phase 2 study of ganitumab or conatumumab in combination with FOLFIRI for second-line treatment of mutant KRAS metastatic colorectal cancer

BACKGROUND

Targeted agents presently available for mutant KRAS metastatic colorectal cancer (mCRC) are bevacizumab and aflibercept. We evaluated the efficacy and safety of conatumumab (an agonistic monoclonal antibody against human death receptor 5) and ganitumab (a monoclonal antibody against the type 1 insulin-like growth factor receptor) combined with standard FOLFIRI chemotherapy as a second-line treatment in patients with mutant KRAS mCRC.

PATIENTS AND METHODS

Patients with mutant KRAS metastatic adenocarcinoma of the colon or rectum refractory to fluoropyrimidine- and oxaliplatin-based chemotherapy were randomized 1 : 1 : 1 to receive intravenous FOLFIRI plus conatumumab 10 mg/kg (Arm A), ganitumab 12 mg/kg (Arm B), or placebo (Arm C) Q2W. The primary end point was progression-free survival (PFS).

RESULTS

In total, 155 patients were randomized. Median PFS in Arms A, B, and C was 6.5 months (HR, 0.69; P = 0.147), 4.5 months (HR, 1.01; P = 0.998), and 4.6 months, respectively; median overall survival was 12.3 months (HR, 0.89; P = 0.650), 12.4 months (HR, 1.27; P = 0.357), and 12.0 months; and objective response rate was 14%, 8%, and 2%. The most common grade ≥3 adverse events in Arms A/B/C included neutropenia (30%/25%/18%) and diarrhea (18%/2%/10%).

CONCLUSIONS

Conatumumab, but not ganitumab, plus FOLFIRI was associated with a trend toward improved PFS. Both combinations had acceptable toxicity.