Does N-acetylcysteine actually clear spike protein from the body?

The short answer is: no, there is no direct human evidence that N-acetylcysteine (NAC) clears spike protein from the body, and the retrieved records do not even study that question.

The evidence block contains exactly one record, an in vitro and tissue study of COVID-19 patients [1]. It shows that SARS-CoV-2 proteins (S, E, M) activate the NLRP3 inflammasome in macrophages and bronchial epithelial cells, and that N-acetylcysteine suppresses that activation in cell culture [1]. That is a mechanism for reducing inflammation, not a mechanism for clearing spike protein. The study measured mRNA and protein expression of inflammasome components in tracheal tissue from critically ill patients, comparing non-COVID controls (n=32) to B.1 (n=31) and B.1.1.7 (n=20) variants [1]. It found higher NLRP3, ASC, CASP1, and IL-1β expression in COVID-19 tissue, strongest in the alpha variant [1]. But it never measured spike protein clearance, viral load, or any outcome after NAC administration in humans.

What this means: NAC might reduce the inflammatory cascade that spike protein triggers, which is a plausible adjunct for COVID-19 severity. But "reduces inflammasome activation in a dish" is not "clears spike protein from the body." Those are different claims separated by the entire gap between cell culture and human pharmacokinetics. No retrieved study measured NAC's effect on spike protein concentration in blood or tissue, no study tracked its half-life or clearance, and no study even attempted to show NAC binds, degrades, or removes the protein. The evidence for NAC as a spike-clearing agent is exactly zero.

The confidence here is high on one point: the claim as stated is unsupported. The evidence is thin, single-study, and in vitro for the NAC effect. If you want to know whether NAC reduces COVID-19 severity through anti-inflammatory action, that is a separate question with some mechanistic plausibility. But "clears spike protein" is not what the science shows, and no retrieved record comes close to demonstrating it.