Titration of signalling output: insights into clinical combinations of MEK and AKT inhibitors

Our results show that sub-optimal inhibition of MEK in combination with AKT is less efficient in inhibiting cellular growth compared to completely inhibiting MEK and AKT alone. The results also show that KRAS mutant cells are more sensitive to a combination of MEK and AKT inhibitors compared to BRAF and PIK3CA mutant cells. Both these findings have clinical implications.

Background

We aimed to understand the relative contributions of inhibiting MEK and AKT on cell growth to guide combinations of these agents.

Materials and methods

A panel of 20 cell lines was exposed to either the MEK inhibitor, PD0325901, or AKT inhibitor, AKT 1/2 inhibitor. p-ERK and p-S6 ELISAs were used to define degrees of MEK and AKT inhibition, respectively. Growth inhibition to different degrees of MEK and AKT inhibition, either singly or in combination using 96-h sulphorhodamine assays was then studied.

Results

A significantly greater growth inhibition was seen in BRAF^M and PIK3CA^M cells upon maximal MEK (P = 0.004) and AKT inhibition (P = 0.038), respectively. KRAS^M and BRAF/PIK3CA/KRAS^WT cells were not significantly more likely to be sensitive to MEK or AKT inhibition. Significant incremental growth inhibition of the combination of MEK + AKT over either MEK or AKT inhibition alone was seen when MEK + AKT was inhibited maximally and not when sub-maximal inhibition of both MEK + AKT was used (11/20 cell lines versus 1/20 cell lines; P = 0.0012).

Conclusions

KRAS^M cells are likely to benefit from combinations of MEK and AKT inhibitors. Sub-maximally inhibiting both MEK and AKT within a combination, in a majority of instances, does not significantly increase growth inhibition compared with maximally inhibiting MEK or AKT alone and alternative phase I trial designs are needed to clinically evaluate such combinations.

AKT inhibition synergistically enhances growth-inhibitory effects of gefitinib and increases apoptosis in non-small cell lung cancer cell lines

OBJECTIVES

EGFR inhibitors are ineffective against most EGFR wild-type non-small cell lung cancer, for which novel treatment strategies are needed. AKT signalling is essential for mediating EGFR survival signals in NSCLC. We evaluated the combination of gefitinib and two different AKT inhibitors, the allosteric inhibitor AKTi-1/2 and the ATP-competitive pan-AKT inhibitor AZD5363, in EGFR-mutant (HCC-827 and PC-9) and -wild-type (NCI-H522, NCI-H1651), non-small cell lung cancer cell lines.

MATERIALS AND METHODS

Drug interaction was studied in two EGFR mutant and two EGFR wild-type non-small cell lung cancer cell lines by calculating combination index (CI) using median effect analysis. The effects on p-EGFR, p-ERK, p-AKT, p-S6 and apoptosis were studied by Western blot analysis.

RESULTS

The combination of gefitinib and AKTi-1/2 or AZD5363 showed synergistic growth inhibition in all cell lines. CI values for the combination of gefitinib and AKTi-1/2 were 0.35 (p=0.0048), 0.56 (p=0.036), 0.75 (p=0.13) and 0.64 (p=0.0003) in NCI-H522, NCI-H1651, HCC-827 and PC-9 cell lines, respectively; CI values of 0.45 (p=0.0087) and 0.22 (p<0.0001) were observed in NCI-H522 and PC-9 cells, respectively, when gefitinib was combined with AZD5363. Additive inhibition of signalling output through AKT and key downstream proteins (S6) and increased apoptosis were demonstrated.

CONCLUSION

Dual inhibition of EGFR and AKT may be a useful up-front strategy for patients with EGFR-mutant and -wild-type non-small cell lung cancer.

Safety, tolerability, pharmacokinetics and pharmacodynamics of AZD8055 in advanced solid tumours and lymphoma

Background:

This study assessed the safety, tolerability, pharmacokinetics and pharmacodynamics of the first-in-class dual mammalian target of rapamycin complex (mTORC)1/mTORC2 inhibitor, AZD8055.

Methods:

Patients with advanced solid malignancies or lymphomas were recruited into this phase I, open-label, dose-escalation study of AZD8055 starting at 10 mg twice-daily oral dosing (BID).

Results:

Forty-nine patients received AZD8055. Dose-limiting toxicities were reported at 40 mg (n=1), 90 mg (n=1) and 120 mg (n=3) BID; all were grade 3 rises in transaminases, reversible in all patients, apart from one who had liver metastases. The maximum tolerated dose was defined as 90 mg BID. The most frequent adverse events assessed to be related to AZD8055 were increased alanine aminotransferase (22%), increased aspartate aminotransferase (22%) and fatigue (16%). AZD8055 was rapidly absorbed (median t_max ∼0.5 h) and exposure increased with increasing doses. Seven patients had stable disease for ⩾4 months. Partial metabolic responses, assessed by fluorodeoxyglucose positron emission tomography, were observed at ⩾40 mg BID (n=8 at day 35).

Conclusion:

The maximum tolerated dose for AZD8055 is 90 mg BID. Apart from elevated transaminases, which occurred at most dose levels, the drug had an acceptable toxicity profile; however, no RECIST responses were seen.

Creatinine clearance is associated with toxicity from molecularly targeted agents in phase I trials

Objectives

This study aimed to evaluate any correlations between baseline creatinine clearance and the development of grade 3/4 toxicities during treatment within oncology phase I trials of molecularly targeted agents where entry criteria mandate a serum creatinine of ≤1.5 × the upper limit of normal.

Methods

Documented toxicity and creatinine clearance (calculated by the Cockcroft-Gault formula) from all patients treated with molecularly targeted agents in the context of phase I trials within our centre over a 5-year period were analyzed.

Results

Data from 722 patients were analyzed; 116 (16%) developed at least one episode of grade 3/4 toxicity. Patients who developed a late-onset (>1 cycle) grade 3/4 toxicity had a lower creatinine clearance than those who did not (82.69 ml/min vs. 98.97 ml/min; p = < 0.001).

Conclusion

Creatinine clearance (even when within normal limits) should be studied as a potential factor influencing late toxicities in the clinical trials of molecularly targeted anti-cancer drugs.

Defining the risk of toxicity in phase I oncology trials of novel molecularly targeted agents: a single centre experience

BACKGROUND

This study defined the risk of serious toxicity in phase I trials of molecularly targeted agents (MTA).

PATIENTS AND METHODS

A retrospective analysis of toxicity data from patients treated in phase I trials of MTAs was carried out to define the rate of treatment-related grade 3/4 toxic effects, deaths and risk factors associated with grade 3 or more toxicity.

RESULTS

Data from 687 patients [median age, 59.1 years (range 12.5-85.5)] treated in 36 trials were analysed. Two hundred and eleven patients were of Eastern Cooperative Oncology Group performance status (PS) zero, 432 of PS one, 38 of PS two and 6 unknown. The rate of grade 3 and 4 events was 14.1% (n=97) and 1.9% (n=13), respectively. Twenty-four percent of events were gastrointestinal, 22% constitutional and 20% metabolic. PS two was associated with a higher risk of toxicity [odds ratio (OR), 2.6; 95% confidence interval (CI) 1.1-6.1; P=0.032] as was receiving >100% of maximum tolerated dose or maximum administered dose (OR 2.5; CI 1.6-3.9; P<0.001). Mortality rate was 0.43% (n=3).

CONCLUSIONS

Therapy with novel MTAs in phase I trials is associated with a moderate risk of significant toxicity. This appears less than in phase I studies involving cytotoxic agents, particularly in relation to grade 4 toxicity. The risk of death is low.