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: Combination versus sequential paclitaxel plus gemcitabine as first-line chemotherapy for women with metastatic breast cancer: a prospective randomized phase II study. paclitaxel (T) plus gemcitabine (G) is an active concomitant combination for the treatment of metastatic breast cancer (MBC). However, the efficacy of sequential administration of these two drugs is unclear. This randomized phase II study was conducted to evaluate the efficacy of T and G administered either as a concomitant or as a sequential regimen in patients with MBC. ### methods Patients with MBC (n=66) were randomized to either receive 6 cycles of concomitant T and G or 4 cycles of T followed by 4 cycles of G, as first line chemotherapy. With no progression, the arms would switch to maintenance with paclitaxel. Progression free survival (PFS) was defined as the primary endpoint; secondary endpoints were the overall response rate (ORR), overall survival (OS), and toxicity. In total, 33 patients were randomized to the concomitant or sequential arms. Patient characteristics were well balanced. The median number of chemotherapy cycles was 6 for the concomitant arm and 8 for the sequential arm. ### results No significant difference was observed in terms of PFS, ORR, and OS. Only 13 (39.4%) patients progressed in the sequential arm. Although there was no significant difference between the two arms (p=0.056),the sequential arm had a remarkable trend of longer PFS than the concomitant arm. Toxicities were manageable and similar in both arms.The incidence of neutropenia was significantly higher in the concomitant arm (90.9%) than in the sequential arm (60.6%). Grade 3 or 4 neutropenia was not significantly different between the two arms. ### conclusions Concomitant and sequential treatment with paclitaxel and gemcitabine had no significant difference in terms of PFS .

sentence: Concomitant and sequential treatment with paclitaxel and gemcitabine had no significant difference in terms of PFS .
[["paclitaxel", "gemcitabine", "COMB"]]