You will be shown a paragraph from a biomedical research article. Your task is to extract all drug combinations appearing in a specific sentence within in the paragraph. Each drug combination should be assigned to one of the following three categories:

- POS: Indicates a positive interaction between the drugs in the combination; for instance, drugs that have an additive or synergistic effect.
- NEG: Indicates a negative interaction between the drugs in the combination; for instance, combining these drugs might result in adverse side effects, or might reduce their efficacy.
- COMB: Indicates that the drugs are given in combination, but the type of interaction between the drugs cannot be determined based on the provided context.

Please format your answer as a json array. Each entry in the array should itself be an array formatted as [<drug_1>, <drug_2>, ..., <drug_n>, <category>] where <category> is one of the three categories listed above and <drug_1>, ..., <drug_n> are drug names copied verbatim from the input sentence. Different combinations may involve different numbers of drugs; in other words, the `n` in <drug_n> may vary.

As an example, the following output describes two extracted drug combinations; one between two drugs, and one between three drugs:

[["artesunate", "artemether", "COMB"], ["Nifedipine", "Labetalol", "Prazosin", "POS"]]

The paragraph and specific sentence are below. You should only extract relationships expressed in the specific sentence; the paragraph is provided for context.

In your output, return only the json array and no other text. If no drug combinations appear, return an empty array `[]`.

paragraph: Synergism of cytotoxic effects of vinorelbine and paclitaxel in vitro. Empiric combinations of vinca alkaloids with taxanes have been recently used in clinical oncology. To enhance the activity of these two classes of agents, we evaluated the sequence and duration of exposure, looking for synergistic effects. Cell lines DU 145, PC 3, LnCaP, LL 86, MCF7wt, and MCF7/ADR (NCI/ADR-RES) were incubated with varying concentrations of paclitaxel or vinorelbine. Cytotoxicity was evaluated by a semiautomated MTT (3-[4,5-dimethylthiazole-2-yl]-2,5-diphenyltetrazolium bromide) method. Synergism or antagonism of these two agents either sequentially or in combination was determined by median effect analysis. Prolonged exposure of cells to either drug enhanced cytotoxic effect. Synergism or antagonism with vinorelbine and paclitaxel were both sequence dependent and cell line specific. In the case of MCF7wt, synergism was seen when a 48-hr exposure to vinorelbine preceded paclitaxel, whereas antagonism was noted when both agents were applied simultaneously or when the sequence was reversed. Concurrent vinorelbine and paclitaxel were synergistic in four of six cell lines when the exposure was extended to 96 hr but not for shorter durations of exposure. Sequential exposure of vinorelbine preceding paclitaxel or prolonged exposure to both agents concurrently needs to be tested clinically to determine whether the antitumor activity of this combination can be enhanced . In addition, these studies suggest concurrent administration of these two agents may lead to a less than optimal cytotoxic result.

sentence: Sequential exposure of vinorelbine preceding paclitaxel or prolonged exposure to both agents concurrently needs to be tested clinically to determine whether the antitumor activity of this combination can be enhanced .
[["vinorelbine", "paclitaxel", "POS"]]