# CJC-1295 Dosage Research — Doses, Routes, and Half-Life in the Primary Literature

> Research-context summary of CJC-1295 dosing parameters: Phase 1 ascending-dose cohorts, GHRH-knockout normalization data, estimated half-life by albumin binding, and route considerations.

The published CJC-1295 pharmacokinetic and pharmacodynamic literature, organized by study species, dose cohort, and route. All values describe research protocols documented in peer-reviewed publications and do not constitute dosing recommendations.

## Doses in the primary literature

All dosing figures on this page come from published research protocols — what was administered in controlled studies, in which species, at which dose level, by which route. The human data consist of three studies: an ascending-dose pharmacokinetic trial using 30, 60, 120, and 180 micrograms per kilogram subcutaneously; a pulsatility study using 60 or 90 micrograms per kilogram; and a proteomic study using the same dose range. The mouse data use 2 micrograms once daily. High variability in the GH response — a two- to tenfold range even within the same dose cohort — is one of the defining features of the human pharmacokinetic record, reflecting the well-documented inter-individual variability in endogenous GH pulsatility. No values here are personal recommendations. CJC-1295 is not approved for human use, and this page makes no suggestion about what any person should take — it documents what investigators administered in controlled research settings and what they observed.

## Pharmacokinetic Framework: Half-Life and the DAC Depot

The most pharmacologically distinctive characteristic of CJC-1295 is its plasma half-life: estimated at 5.8 to 8.1 days in healthy human adults following subcutaneous injection, derived from pharmacokinetic modeling in the Teichman et al. (2006) Phase 1 study [2]. For comparison, native GHRH(1–29) — the unmodified peptide occupying the same receptor — has a plasma half-life of approximately 10 to 13 minutes [6]. The approximately 800-fold extension of plasma persistence produced by covalent albumin conjugation via the maleimidopropionic acid Drug Affinity Complex (DAC) moiety is therefore the central pharmacokinetic fact about this compound class.

Albumin's plasma half-life of approximately 19 days functions as the pharmacokinetic ceiling — CJC-1295's effective half-life is governed by the rate of peptide release from the albumin depot and the rate of albumin turnover. The maleimide-thiol bond is stable under physiological conditions, meaning that release occurs through albumin catabolism and possible secondary protease activity rather than spontaneous hydrolysis [6]. In vivo stability against DPP-IV degradation is enhanced by the D-Ala substitution at position 2, which eliminates the canonical DPP-IV cleavage site present in native GHRH [1].

For urinary metabolite detection purposes, CJC-1295 metabolites degrade rapidly at temperatures above 4°C and at pH below 7 [11]. This thermal and pH instability of urinary species has practical implications for sample handling in analytical research and anti-doping protocols — samples require immediate refrigeration to preserve detectable metabolite concentrations [11]. The albumin-conjugated circulating form is not readily detected by standard mass spectrometry without prior immunoaffinity enrichment [8][9].

## Human Research Doses: Phase 1 Ascending-Dose Data

The Phase 1 ascending-dose study by Teichman et al. (2006) evaluated subcutaneous doses of 30, 60, 120, and 180 mcg/kg in healthy adult humans [2]. The 30 mcg/kg and 60 mcg/kg cohorts produced the most favorable pharmacodynamic-to-tolerability profiles in the reported ascending-dose design. At these dose levels, mean plasma GH concentrations were elevated 2- to 10-fold and remained above baseline for 6 or more days post-injection. IGF-1 increased 1.5- to 3-fold with elevations persisting 9 to 11 days. No serious adverse reactions were observed in these cohorts. Multiple-dose administration — biweekly injections — sustained IGF-1 above baseline for up to 28 days [2], consistent with predicted accumulation from a depot-forming agent with a half-life in the 6-to-8-day range.

Ionescu and Frohman (2006) administered single subcutaneous injections of 60 or 90 mcg/kg to healthy men aged 20 to 40 [3]. Both dose levels produced substantially similar pulsatility outcomes — GH pulse frequency and magnitude were preserved — and the study did not report a statistically significant difference between the 60 and 90 mcg/kg groups on these measures. Basal GH rose 7.5-fold; overall mean GH increased 46%; IGF-1 increased 45% [3]. The absence of a significant dose-response difference between 60 and 90 mcg/kg on pulsatility endpoints suggests that, within this range, the compound's receptor-engagement pharmacodynamics may operate on a plateau rather than a linear dose-response segment for the specific outcomes studied.

Proteomic analysis by Sackmann-Sala et al. (2009) was conducted in 11 healthy adult males receiving 60 to 90 mcg/kg single subcutaneous doses [5]. No dose-specific pharmacodynamic comparison was reported in this study, which focused on characterizing protein profile changes rather than dose-response relationships. The combined human pharmacokinetic and pharmacodynamic data are therefore limited in scope: two Phase 1 studies in healthy young adults, with ascending-dose data only up to 180 mcg/kg, and no data in GH-deficient, elderly, or pediatric populations.

High inter-individual variability is a notable feature of the human pharmacodynamic data. The 2- to 10-fold range of GH elevation reported by Teichman et al. at the 30 and 60 mcg/kg doses [2] indicates substantial subject-to-subject variability in GH axis responsiveness — a finding consistent with the well-documented inter-individual variability in endogenous GH pulsatility and the complex multilevel negative feedback of the GH/IGF-1 axis.

## Animal Model Doses: GHRH-Knockout Normalization Data

In C57BL GHRH-knockout mice — animals lacking endogenous GHRH and exhibiting growth retardation — Alba et al. (2006) administered CJC-1295 subcutaneously at 2 mcg once daily [4]. This once-daily regimen normalized body weight, body length, bone development, and body composition in treated animals over the study period. Pituitary total RNA and GH mRNA increased significantly, and immunohistochemical analysis confirmed somatotroph cell proliferation in the CJC-1295-treated group [4].

Dosing at every-48-hour or every-72-hour intervals in the same GHRH-knockout model produced diminished effects compared to the once-daily regimen, establishing a schedule-dependence relationship for normalization outcomes in this model [4]. The mechanistic inference — that more frequent stimulation of the GHRH receptor produces superior normalization in a GHRH-deficient context — is consistent with the receptor's known signaling kinetics, though the pharmacokinetic properties of CJC-1295's albumin-depot release in mice may differ from those in larger mammals and humans.

The rat pharmacology established by Jette et al. (2005) did not report specific mcg/kg doses in the abstract; the study documented a 4-fold GH AUC increase over two hours and plasma persistence beyond 72 hours by Western blot, confirming pharmacological activity without establishing a dose-response curve in the Sprague-Dawley rat model [1].

In the equine anti-doping pharmacology literature, Timms et al. (2019) administered CJC-1295 to thoroughbred racehorses at doses not specified in the available abstract, establishing an immunoassay screening threshold of 50 pg/mL in equine plasma [8]. This equine administration data is relevant to veterinary anti-doping research rather than to the compound's human pharmacology profile.

## Route Considerations and Related Analog Context

All human research involving CJC-1295 employed the subcutaneous route of administration [2][3][5]. Intravenous administration appears only in the diagnostic GHRH/arginine stimulation test literature — a clinical diagnostic procedure using native GHRH or structural analogs, unrelated to CJC-1295 specifically — and in the equine anti-doping context [8]. No published human data support intravenous administration of CJC-1295.

A structurally related GHRH analog, tesamorelin (GHRH 1–44 with a trans-3-hexenoic acid modification), was studied in healthy men at 2 mg subcutaneous once daily for two weeks by Stanley et al. (2011) [14]. This regimen produced mean overnight GH increases of 0.5 mcg/L (P = 0.004), GH pulse area increases (P = 0.001), and IGF-1 elevation to 181 ± 22 mcg/L (P < 0.0001), without significant changes in fasting glucose or insulin-stimulated glucose uptake [14]. Effects reversed within two weeks of withdrawal. This tesamorelin data, from a distinct compound with its own regulatory history, provides mechanistic context for the GHRH analog class as a whole — particularly regarding glucose metabolism effects at moderate GH/IGF-1 axis activation levels — but should not be conflated with CJC-1295's specific pharmacological profile.

The combination of CJC-1295 with ipamorelin — a GH secretagogue acting at the ghrelin receptor, a pathway complementary to the GHRH receptor — showed significantly improved maximum tetanic tension in murine glucocorticoid-induced muscle atrophy models compared to vehicle and to either compound alone [15]. The mechanistic rationale is additive: GHRH analogs increase GH pulse amplitude via pituitary somatotroph stimulation, while GH secretagogues such as ipamorelin increase pulse frequency via the hypothalamic ghrelin axis. Both pathways converge on somatotroph GH output by complementary mechanisms [15]. This combination has been studied only in murine models and has not been evaluated in controlled human trials.

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An independent scholarly digest of the peer-reviewed CJC-1295 literature — not a clinic, not a vendor, not medical advice.