# CJC-1295 Dosage Research Context — Half-Life, Routes, and Study Protocols > Research-context summary of CJC-1295 dose ranges studied in published trials, half-life data (5.8–8.1 days), routes of administration, and comparison with Modified GRF 1-29. — not dosing guidance. All dose information on this page is drawn directly from published studies. It describes research protocols — not recommendations for any use. ## The short version The published human doses for CJC-1295 come from the same 2006 research trial: 30, 60, 90, and 120 micrograms per kilogram of body weight, given by subcutaneous injection [1][2][3]. That is the entire human dosing database. There are no long-term human studies, and there is no clinically established dose for any indication, because CJC-1295 is not an approved drug. The long half-life — about six to eight days — means even a single injection elevates GH and IGF-1 for over a week. The trial used once-weekly and twice-weekly schedules [2]. 'Doses' circulating online for athletic or aesthetic use are not drawn from controlled human research. The distinction between the long-acting DAC form and the short-acting no-DAC form (Modified GRF 1-29) matters: DAC accumulates with repeated dosing in a way the short-acting form does not [13]. ## Half-life: the defining pharmacokinetic feature CJC-1295's most clinically distinctive characteristic is its plasma half-life of 5.8–8.1 days in humans [3]. To appreciate what this means, it helps to look at the full spectrum: - Native GHRH (endogenous): approximately 7–10 minutes, due to rapid DPP-IV cleavage. - Modified GRF 1-29 (CJC-1295 without DAC): approximately 30 minutes, because the four amino acid substitutions confer DPP-IV resistance but without the albumin-binding moiety. - CJC-1295 (with DAC): 5.8–8.1 days, because the albumin-binding DAC mechanism creates a macromolecular depot that releases the peptide slowly over days [13]. This is not a small difference. A half-life of 5.8–8.1 days is roughly 1,200 times longer than native GHRH. It is the property that allowed Teichman and colleagues to study once-weekly and twice-weekly subcutaneous dosing in their 2006 trial — intervals that would be meaningless for native GHRH [3]. The albumin-binding mechanism is the pharmacological explanation. After subcutaneous injection, the maleimide group on CJC-1295's C-terminus forms a covalent thioether bond with Cys34 of circulating serum albumin, confirmed by Western blot within 15 minutes of injection in rat studies [12]. The resulting ~67 kDa conjugate cannot be cleared by glomerular filtration and is resistant to proteolytic degradation. Albumin's own half-life in humans is approximately 19 days, so the CJC-1295/albumin conjugate circulates as a slowly releasing reservoir rather than a bolus. This extended half-life also means that CJC-1295 elevates IGF-1 in a sustained rather than pulsatile pattern. In the Teichman trial, single-dose IGF-1 elevation was detectable for 9–11 days at the tested doses [1]. The long-term implications of sustained (as opposed to physiologically pulsatile) IGF-1 elevation are not fully characterized in humans, which is one of the open questions flagged in the research literature [17]. ## Doses studied in human research The human pharmacokinetic and pharmacodynamic data for CJC-1295 come primarily from the Teichman 2006 trial [1][2][3]. Doses studied were: - **30 μg/kg subcutaneous** — lowest dose studied; produced dose-dependent GH and IGF-1 elevation with the most favorable tolerability profile. - **60 μg/kg subcutaneous** — studied both as a single dose and as a weekly or twice-weekly multiple-dose protocol. Produced robust GH and IGF-1 elevation; well-tolerated in the trial context. - **90 μg/kg subcutaneous** — studied in the proteomic biomarker sub-study by Sackmann-Sala et al. [8]. - **120 μg/kg subcutaneous** — highest dose studied; produced greater GH area-under-the-curve increases but was associated with more injection-site reactions (redness, induration). Still within the range of no serious adverse events in the Phase 1/2 cohort. In the multiple-dose arm, once-weekly and twice-weekly injections at 30–60 μg/kg maintained IGF-1 above baseline for up to 28 days after the final dose [2]. No dose study in humans has evaluated daily administration — the long half-life makes it pharmacokinetically unnecessary, and cumulative IGF-1 build-up at daily intervals would be expected. All human studies used subcutaneous injection as the route of administration. Intravenous administration was used in some pharmacokinetic characterization studies, but the subcutaneous route is the one evaluated across all tolerability and efficacy data [1][2][3]. The Sackmann-Sala 2009 proteomic study [8] administered 60–90 μg/kg to 11 healthy men in a single-dose protocol, producing the downstream serum protein fraction changes described in the research literature. This study was not a dose-escalation trial; it used a sub-range of the Teichman doses to examine biomarker changes rather than tolerability. Important context: the entire human data set is derived from two short-term trials (28 days in the multiple-dose arm, 49 days in the extended observation period) in healthy adult volunteers. There are no long-term human safety studies. The FDA PCAC December 2024 briefing characterized the human safety data as limited [14]. ## Animal model doses In GHRH-knockout mouse studies, once-daily subcutaneous administration at 2 μg/day (without conversion to body-weight-adjusted kg doses in the primary publication) normalized growth parameters over a five-week course [4]. Dosing frequency was found to matter: 24-hour intervals produced greater normalization of body weight, body length, and pituitary GH mRNA expression than 48-hour or 72-hour intervals [5]. This frequency-dependence reflects the sustained but not flat pharmacokinetics — even with the long half-life, more frequent dosing maintained a higher average GHRHR occupancy in the knockout model. In Sprague Dawley rat pharmacokinetic studies, equimolar doses were used for comparative GH AUC analysis against unconjugated GRF(1-29) [6]. The rat studies also confirmed Western blot-detectable albumin conjugation within 15 minutes of injection, persisting beyond 24 hours [12]. The 2026 gerontology review documented CJC-1295 combined with ipamorelin in murine glucocorticoid-induced muscle loss models, with significant improvement in maximum tetanic tension [18]. Specific dose values for this combination were not reported in the primary source as summarized in that review. Animal-to-human dose extrapolation has significant limitations. Differences in body weight, allometric scaling, DPP-IV activity, albumin concentration and turnover rates, and GH pulsatility patterns between rodents and humans make direct numerical comparison of rodent doses and human doses unreliable. ## Modified GRF 1-29: a closely related but distinct compound Modified GRF 1-29 — frequently labeled 'CJC-1295 without DAC' in commercial research contexts — shares CJC-1295's four DPP-IV-resistant amino acid substitutions but lacks the albumin-binding DAC moiety [13]. This distinction has significant pharmacokinetic consequences: - Half-life: approximately 30 minutes (Mod-GRF 1-29) versus 5.8–8.1 days (CJC-1295 with DAC). - GH secretion profile: Mod-GRF 1-29 produces sharper, shorter-duration GH pulses more closely mimicking a natural GHRH pulse. CJC-1295 DAC produces a sustained elevation of baseline GH with pulsatility preserved but at a chronically elevated mean. - Research dosing intervals: Mod-GRF 1-29 would require multiple daily administrations to maintain receptor occupancy, given its 30-minute half-life. CJC-1295 DAC enables once- or twice-weekly intervals [3]. The labeling convention 'CJC-1295 without DAC' is widespread but is a misnomer that the research literature has flagged as a source of protocol confusion [13]. The two compounds are not interchangeable in research design. A 2010 review paper on Class II G-protein-coupled receptor ligand modification noted both the DPP-IV resistance and DAC mechanisms as distinct contributions to half-life extension [13]. Both Mod-GRF 1-29 and CJC-1295 DAC appear on FDA regulatory evaluation lists and both are prohibited by WADA under S2.2.4. Neither is FDA-approved. ## Storage and stability Published pharmacokinetic data and manufacturer specifications describe CJC-1295 as lyophilized powder that is stored at –20°C and reconstituted in bacteriostatic water prior to use. Research vendors report purity >95% by HPLC under proper cold-chain conditions, though independent analysis of grey-market preparations has found purity variance from 91.2% to 99.1% even in products labeled >95% pure. The maleimide-albumin covalent bond is stable once formed in vivo. However, the maleimide group on the reconstituted peptide prior to injection is reactive and can degrade if the reconstituted product is stored improperly or at elevated temperatures. Impurities in albumin-binding peptides carry immunogenicity risk — a concern flagged by the FDA PCAC in December 2024 as one factor in their negative vote on 503A inclusion [14]. Anti-doping research has confirmed that the albumin-conjugated form of CJC-1295 is not amenable to direct mass spectrometry because the conjugate is too large for standard LC-MS/MS workflows. Validated detection requires either immuno-PCR (which can detect the DAC-bound form at 0.8 pg/mL [10]) or immunoaffinity capture followed by enzymatic digestion before LC-MS/MS (detecting at 180 pg/mL [11]). This analytical challenge has implications for purity testing of research preparations — standard mass spec may miss the albumin-conjugated fraction or its degradation products. --- A research digest of peer-reviewed literature and the regulatory record — not a clinic, not a vendor, not medical advice.