Introduction
In the past several decades, outbreaks of epidemics, such as SARS, Ebola, MERS, Zika virus, and the still rampant COVID-19, have become surprisingly more frequent, posing an egregious threat to public health and safety. Despite the challenges in developing biologics in a shorter time than usual, the high efficacy and accuracy in neutralizing and containing pathogens have made these biologics more and more favored by both academic research and the pharmaceutical industry (Baum et al., 2020; Brouwer et al., 2020; Cao et al., 2020; Gao et al., 2020; Hansen et al., 2020; Ju et al., 2020; Lan et al., 2020; Nyon et al., 2018; Pinto et al. 2020; Rogers et al., 2020; Shi et al., 2020; Wang et al., 2020; Zhang et al., 2020). This change of preference would be quite unrealistic without vast experiences of developing countless biologics, as witnessed by the global pharmaceutical industry (Li et al., 2010; Kunert et al., 2016). However, even though there have been many different types of CMC strategies in accommodating all kinds of biologics development scenarios, the currently fastest CMC timeline from DNA to IND of 10- or 12-months are yet insufficient against the challenge of a global public health emergency. How to conduct the CMC activities with greater time-efficiency without compromising product quality while meeting regulatory requirements has put both the biologics development projects and the business interests under test (Sempowski et al., 2020).
Traditional CMC activities contain cell line development (CLD) and process development, including upstream, downstream, formulation, and analytical method development before toxicology and GMP production. To find the most appropriate clone from hundreds or thousands of clone candidates, usually, at least 4 months are required for exhaustive screening efforts during cell line development. Meanwhile, process development dedicated to the specific molecules, including cell culture process, purification process, formulation, and assay development, requires approximately 3 months before at least one round of process qualification with the final clone. To save these 3 months from painstaking developments and qualifications of process and assay, pandemic neutralizing antibody projects usually favor the molecules with less complexity, or the molecules with established platform architecture, since it is beneficial to take advantage of the platform process, which helps to avoid the complications of process or assay incompatibility and the uncertain time cost for the traditional tedious but indispensable developments and qualifications (Kelley, 2020; Bolisetty et al., 2020). Another recent advance in time-efficient strategy is by shifting the materials produced for pre-clinical toxicological study from by the selected top clone to an appropriate stable cell pool, which has been elaborated and exercised by several leading pharmaceutical companies (Bolisetty et al., 2020; Fan et al., 2017; Hu et al., 2017; Munro et al., 2017; Rajendra et al., 2017; Scarcelli et al., 2017; Wright et al., 2017). Typically, performing one round of limited-dilution cloning or FACS cloning with the subsequent clone selection requires at least 7 weeks beyond the establishment of a stable cell pool. Bringing the pre-clinical toxicology ahead of the traditional schedule replaces the speed-limiting activities to how to wisely unfold the CMC paths. With successful precedents of such practice, it is feasible to leverage the acceleration strategies with respect to the life-saving pre-clinical toxicological and Phase I first-in-human study against the global public health emergency. Because of the returning of the critical path to CMC, together with limited time for the process, assay, and formulation optimization, the beginning of a biologics CMC, cell line development, has a crucial significance for the subsequent manufacturing planning and decisions, which is also the perspective from which we prefer to rethink and reshape the CMC strategies.
Here we described a series of key steps to accelerating the overall CMC timeline per the CLD scope. First of all, transfections were performed under cGMP conditions and recovered stable cell pools were used directly for toxicology and cGMP production. Second, high-throughput clone screening was implemented to obtain top clones, then thorough clone culturing evaluation and preliminary cell line stability study with these selected top clones were carried out in parallel. Next, the clone with the closest product quality from the culturing evaluation to the preceding cGMP pool material was selected as the final clone for master cell bank (MCB) creation and the manufacturing henceforward. Meanwhile, the platform process should be tested whenever possible for qualification and optimization with no time to squander.