Potential anti-COVID-19 agents, cepharanthine and nelfinavir, and their usage for combination treatment by Ohashi, H, Watashi, K, Saso, W, Shionoya, K, Iwanami, S, Hirokawa, T, Shirai, T, Kanaya, S, Ito, Y, Kim, KS, Nomura, T, Suzuki, T, Nishioka, K, Ando, S, Ejima, K, Koizumi, Y, Tanaka, T, Aoki, S, Kuramochi, K, Suzuki, T, Hashiguchi, T, Maenaka, K, Matano, T, Muramatsu, M, Saijo, M, Aihara, K, Iwami, S, Takeda, M, McKeating, JA, Wakita, T