BackgroundA promising novel cell-free bioactive formulation for articular cartilage regeneration, called BIOF2, has recently been tested in pre-clinical trials. The aim of the present study was to evaluate the efficacy and safety of BIOF2 for intra-articular application in patients with severe osteoarthritis of the knee.MethodsA prospective, randomized, 3-arm, parallel group clinical trial was conducted. It included 24 patients with severe osteoarthritis of the knee (WOMAC score 65.9 ± 17). Before they entered the study, all the patients were under osteoarthritis control through the standard treatment with nonsteroidal anti-inflammatory drugs (NSAIDs), prescribed by their family physician. Patients were distributed into three groups of 8 patients each (intra-articular BIOF2, total joint arthroplasty, or conservative treatment with NSAIDs alone). The WOMAC score, RAPID3 score, and Rasmussen clinical score were evaluated before treatment and at months 3, 6, and 12. BIOF2 was applied at months 0, 3, and 6. Complete blood count and blood chemistry parameters were determined in the BIOF2 group before treatment, at 72 h, and at months 1, 3, 6, and 12. In addition, articular cartilage volume was evaluated (according to MRI) at the beginning of the study and at month 12.ResultsThe NSAID group showed no improvement at follow-up. Arthroplasty and BIOF2 treatments showed significant improvement in all the scoring scales starting at month 3. There were no statistically significant differences between the BIOF2 group and the arthroplasty group at month 6 (WOMAC score: 19.3 ± 18 vs 4.3 ± 5; P = 0.24) or month 12 (WOMAC score: 15.6 ± 15 vs 15.7 ± 17; P = 1.0). Arthroplasty and BIOF2 were successful at month 12 (according to a WOMAC score: ≤ 16) in 75% of the patients and the daily use of NSAIDs was reduced, compared with the group treated exclusively with NSAIDs (RR = 0.33, 95% CI 0.12–0.87, P = 0.02. This result was the same for BIOF2 vs NSAIDs and arthroplasty vs NSAIDs). BIOF2 significantly increased the articular cartilage by 22% (26.1 ± 10 vs 31.9 ± 10 cm2, P < 0.001) and produced a significant reduction in serum lipids. BIOF2 was well tolerated, causing slight-to-moderate pain only upon application.ConclusionsThe intra-articular application of the new bioactive cell-free formulation (BIOF2) was well tolerated and showed no significative differences with arthroplasty for the treatment of severe osteoarthritis of the knee. BIOF2 can regenerate articular cartilage and is an easily implemented alternative therapy for the treatment of osteoarthritis.Trial registration Cuban Public Registry of Clinical Trials (RPCEC) Database RPCEC00000250. Registered 08/15/2017—Retrospectively registered, http://rpcec.sld.cu/en/trials/RPCEC00000250-En.Electronic supplementary materialThe online version of this article (10.1186/s40001-018-0349-2) contains supplementary material, which is available to authorized users.