The O-15(alpha,gamma) reaction could offer an escape from the hot-CNO cycle if its cross-section at the relevant energies is sufficiently high. In order to indirectly measure it, an experiment based on the Ne-18(d,p) process was performed in Louvain la Neuve.
Cherubini, S., Galster, W., Graulich, JS., Leleux, P., Loiselet, M., Musumarra, A., Ninane, A., Ryckewaert, G., Vervier, J., Aliotta, M., Figuera, P., Lattuada, M., Pellegriti, M., Spitaleri, C., Davinson, T., Di Pietro, A., Laird, A., Ostrowski, A., Shotter, AC., et al. (2001). The O-15(alpha,gamma)Ne-19* reaction using a Ne-18 radioactive beam. Nuclear Physics, Section A, 688(1-2), 465C-467C. https://doi.org/10.1016/S0375-9474(01)00757-6 (Original work published 2001)