Figure 8: Brigatinib combined with cetuximab or panitumumab synergistically suppressed the growth of EGFR-C797S/T790M/del19-expressing cells in vivo.
(a,b) PC9 cells expressing EGFR-C797S/T790M/del19 were subcutaneously implanted into Balb-c nu/nu mice. When the average tumour volume reached ∼200 mm3, the mice were randomized into vehicle control or treatment groups (50 mg kg−1 of osimertinib, 75 mg kg−1 of brigatinib, 1 mg per mouse of cetuximab three times a week or 75 mg kg−1 of brigatinib combined with cetuximab administered as previously described) and treated once daily by oral gavage for the indicated period. Tumour volume (V) was calculated as 0.5 × length × width2, and body weights (B.W.) of mice were measured twice weekly.; N=6. Results are expressed as mean±s.d. The significance of difference between the mean tumour volume of control and of brigatinib on day 7, between brigatinib and brigatinib+cetuximab on day 23, respectively, are calculated by Mann–Whitney U test (**P<0.01). (c) Survival periods of mice in each treatment arm were demonstrated using the Kaplan–Meier curve. (d) Phosphorylation of EGFR and its downstream signalling in two tumour samples obtained from each group were evaluated using western blotting. (e,f) In vivo experiment of PC9 triple-mutant cells following a similar protocol as in Fig. 8a–b, using panitumumab 0.5 mg per mouse two times a week administered peritoneally instead of cetuximab.; N=6. Results are expressed as mean±s.d. The significance of difference between the mean tumour volume of control and of brigatinib on day 16, between brigatinib and brigatinib+panitumumab on day 23, respectively, are calculated by Mann–Whitney U test (**P<0.01). (g) A Kaplan–Meier curve of the survival of the mice in each treatment arm. (h) Phosphorylation of EGFR and its downstream signalling in two tumour samples obtained from xenografts of PC9-triple mutant cells treated for 8 days with the indicated drugs (brigatinib: 75 mg kg−1 daily, administered orally; panitumumab: 0.5 mg per mouse two times a week, administered peritoneally) were assessed by western blotting with the indicated antibodies.
