Next-Generation Covalent Irreversible Kinase Inhibitors in NSCLC: Focus on Afatinib

First-generation, reversible epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs), erlotinib and gefitinib, represented an important addition to the treatment armamentarium for non-small-cell lung cancer (NSCLC) patients with activating EGFR mutations. However, all patients inevitably develop acquired resistance to these agents, primarily due to secondary EGFR mutations, molecular aberrations affecting other signaling pathways, or transformation to small-cell histology. It was hypothesized that development of second-generation TKIs with broader inhibitory profiles could confer longer-lasting clinical activity and overcome acquired resistance to first-generation inhibitors. Here, we review the development of afatinib, an irreversible ErbB family blocker that potently inhibits signaling of all homodimers and heterodimers formed by the EGFR, human epidermal growth factor receptor (HER)-2, HER3, and HER4 receptors. In two phase III trials in patients with EGFR mutation-positive NSCLC, first-line afatinib significantly improved progression-free survival (PFS) and health-related quality of life versus standard-of-care chemotherapy. Moreover, in preplanned sub-analyses, afatinib significantly improved overall survival in patients harboring EGFR Del19 mutations. Afatinib has also demonstrated clinical activity in NSCLC patients who had progressed on erlotinib/gefitinib, particularly when combined with cetuximab, and offers ‘treatment beyond progression’ benefit when combined with paclitaxel versus chemotherapy alone. Furthermore, a recent phase III study demonstrated that PFS was significantly improved with afatinib versus erlotinib for the second-line treatment of patients with squamous cell carcinoma of the lung. The activity of afatinib in both first-line and relapsed/refractory settings may reflect its ability to irreversibly inhibit all ErbB family members. Afatinib has a well-defined safety profile with characteristic gastrointestinal (diarrhea, stomatitis) and cutaneous (rash/acne) adverse events.

A phase Ib, open-label study to assess the safety of continuous oral treatment with afatinib in combination with two chemotherapy regimens: cisplatin plus paclitaxel and cisplatin plus 5-fluorouracil, in patients with advanced solid tumors

BACKGROUND

In this phase Ib, dose-escalation study, the oral irreversible ErbB family blocker afatinib (BIBW 2992) was combined with cisplatin (Cadila Healthcare Ltd, Ahmedabad, India) 50 or 75 mg/m(2)/paclitaxel (Bristol-Myers Squibb Pharmaceuticals Ltd, New York, USA) (Taxol)175 mg/m(2) (regimen A) or cisplatin 75-100 mg/m(2)/5-fluorouracil 750-1000 mg/m(2) (regimen B) in patients with advanced solid tumors.

PATIENTS AND METHODS

The primary objective was to assess dose-limiting toxicities (DLTs) during cycle 1 for each regimen, from which the maximum tolerated dose (MTD) was determined. Patients received once daily oral afatinib 20, 30, 40 or 50 mg in 21-day cycles (3 + 3 design).

RESULTS

The MTD for afatinib in regimens A (n = 26) and B (n = 21) was determined as 20 mg and 30 mg following DLTs in five and four patients in cycle 1, respectively. Most frequent adverse events (AEs, any grade) were diarrhea and nausea. Disease control was observed in 54% and 29% of patients in regimens A and B, respectively. Plasma sampling suggested no relevant pharmacokinetic interaction between afatinib and the chemotherapeutic agents.

CONCLUSIONS

The MTD of afatinib was 20 mg with cisplatin-paclitaxel and 30 mg with cisplatin-5-fluorouracil. Pre-emptive management of side-effects is important to maintain adequate safety and tolerability. Both combinations showed antitumor activity across tumor types and lines of prior treatment.

Afatinib pharmacokinetics and metabolism after oral administration to healthy male volunteers

PURPOSE

To investigate the pharmacokinetics, metabolism and tolerability of afatinib (BIBW 2992), an oral irreversible ErbB family blocker, in healthy male volunteers.

METHODS

In this open-label, single-center study, 8 healthy male volunteers received a single oral dose of 15 mg [(14)C]-radiolabeled afatinib (equivalent to 22.2 mg of the dimaleinate salt) as a solution. Blood, urine and fecal samples were collected for at least 96 hours (h) after dosing. Plasma and urine concentrations of afatinib were analyzed using high-performance liquid chromatography-tandem mass spectrometry. [(14)C]-radioactivity levels in plasma, whole blood, urine and feces were measured by liquid scintillation counting methods. Metabolite patterns were assessed by high-performance liquid chromatography.

RESULTS

[(14)C]-radioactivity was mainly excreted via feces (85.4%). Overall recovery of [(14)C]-radioactivity was 89.5%, indicative of a complete mass balance. Afatinib was slowly absorbed, with maximum plasma concentrations achieved at a median of 6 h after dosing, declining thereafter in a biexponential manner. The geometric mean terminal half-life of afatinib was 33.9 h in plasma and longer for [(14)C]-radioactivity in plasma and whole blood. Apparent total body clearance for afatinib was high (geometric mean 1,530 mL/min). The high volume of distribution (4,500 L) in plasma may indicate a high tissue distribution. Afatinib was metabolized to only a minor extent, with the main metabolite afatinib covalently bound to plasma proteins. Oxidative metabolism mediated via cytochrome P-450 was of negligible importance for the elimination of afatinib. Afatinib was well tolerated.

CONCLUSIONS

Afatinib displayed a complete mass balance with the main route of excretion via feces. Afatinib undergoes minimal metabolism.

Afatinib (BIBW 2992) development in non-small-cell lung cancer

Afatinib (BIBW 2992), a novel aniline-quinazoline derivative, irreversibly and equipotently targets the intrinsic kinase activity of all active ErbB receptor family members. Preclinical results show that afatinib is effective in lung cancer models, including those with EGF receptor (EGFR) mutations resistant to reversible first-generation EGFR inhibitors. Afatinib is being investigated in the LUX-Lung program, which will evaluate afatinib as a first-line treatment in patients with EGFR-activating mutations (LUX-Lung 2, 3 and 6) and as a second- or third-line treatment in patients that have acquired resistance to gefitinib and/or erlotinib (LUX-Lung 1, 4 and 5). LUX-Lung 1 and 2 have demonstrated, within their respective target groups, a significant increase in the disease control rate of 58 and 86%, respectively, and significant prolongation of progression-free survival. Further Phase III clinical trials are currently ongoing to assess afatinib in combination with paclitaxel (LUX-Lung 5), and compared with cisplatin/pemetrexed (LUX-Lung 3) or cisplatin/gemcitabine (LUX-Lung 6).