LIMITX Products in Development

LIMITX technology is intended to address an oral Excessive Tablet Abuse (ETA) or accidental consumption of multiple tablets and provide a margin of safety during accidental over-ingestion of tablets. LIMITX is also expected to exhibit barriers to abuse by snorting and injection.


The FDA’s 2015 Guidance singles out immediate-release combination products with acetaminophen as being predominately abused by the oral route and that reducing nasal snorting of these products may not be meaningful. We currently have the following products in development utilizing our LIMITX Technology:

  • Immediate-release hydromorphone HCl (LTX-04)
  • Immediate-release hydrocodone bitartrate/APAP (LTX-03)
  • Immediate-release oxycodone HCl (LTX-01) & (LTX-02)


The initial LTX-04 clinical study, Study AP-LTX-400, or Study 400, was a two cohort, open label, crossover design pharmacokinetic study in healthy adult subjects. study 400 measured the rate and extent of absorption of the active drug ingredient into the bloodstream with the maximum concentration, or Cmax, typically associated with an increase in drug abuse. Cohort 1 enrolled 30 subjects who were randomized into three subgroups of 10 taking either 1, 2 or 3 tablets. Each subgroup subject orally swallowed the planned number of tablets in a randomized manner taking single doses of two different test formulations of LTX-04 (designated as LTX-04P and LTX-04S and distinguished by their respective acid neutralizing capacity) and Purdue Pharma’s marketed drug Dilaudid® as a comparator. The 1, 2 and 3 tablets subgroups in Cohort 1 completed 8, 10 and 8 subjects, respectively.

Cohort 2 enrolled 30 subjects who were randomized into three subgroups of 10 taking either 4, 6 or 8 tablets. Each subgroup subject orally swallowed the planned number of tablets in a randomized manner taking single doses of LTX-04P and the marketed drug Dilaudid as a comparator. The 4, 6 and 8 tablets subgroups in Cohort 2 completed 8, 9 and 8 subjects, respectively.

All tablets contained 2mg of hydromorphone hydrochloride. All subjects received doses of naltrexone and there was a one week washout between doses. Blood samples were taken at pre-designated time-points after dosing and were subsequently analyzed for the concentration of hydromorphone contained in the sample. All subjects in Cohort 1 had continuous pH (a measure of acid concentration) monitoring of their gastric fluid. The objective of Cohort 1 was to determine if adequate active drug entered the blood stream when one or two LIMITX tablets were swallowed and to begin assessing the ability of the LIMITX Technology to start retarding the release of active ingredients when three tablets are ingested. The objective of Cohort 2 was to further explore the extent the release of the hydromorphone active ingredient from LTX-04P tablets is retarded as the dose level increases to abuse levels. A safety assessment of LIMITX Hydromorphone will be made from both study cohorts.

The topline interim results from Study 400 test formulation LTX-04P, successfully demonstrated the release of the active opioid ingredient was reduced when three or more intact tablets were ingested, but that additional formulation development will be required for LTX-04P to deliver a sufficient amount of the active ingredient to patients when one or two tablets are administered. Specifically, the topline interim results of Study 400 demonstrated:

  • Subjects in Study 400 had a approximate 20% reduction in relative Cmax (maximum plasma concentration of drug) when 3 or more tablets were ingested as shown in the table below.
  • All Subjects in Cohort 2 had extent of drug absorption (measured by AUC) for LTX-04P comparable to Dilaudid when the same number of tablets were ingested. Likewise, the time to maximum plasma concentration, or Tmax, was comparable at all doses to Dilaudid.
  • Subjects taking one or two tablets of both LTX-04 test formulations had comparable extent of drug absorption (measured by AUC) as the same number of tablets of Dilaudid. However, these tablets delivered approximately 50% less peak plasma concentration (Cmax) than Dilaudid. As such, the LTX-04 test formulations were considered to not have achieved equivalent blood levels of drug and will require further development. All study drugs were generally well tolerated and no serious adverse events were observed.

Further analysis of the 3, 4, 6 and 8 tablet subgroups in Study 400 identified a subpopulation of patients in which LTX-04P appeared to demonstrate enhanced reduction in drug absorption as compared to Dilaudid. This subpopulation is characterized by their propensity to absorb the opioid in Dilaudid quickly, reaching maximum drug concentration in the blood in 30 minutes or less, while, on average, having maximum blood levels of drug 1.8 times that of the slower drug absorbing subjects. This subpopulation may represent a more vulnerable abuse population as speed of drug absorption and higher peak drug levels in the blood are typically associated with more drug abuse and possibly addiction.

In the faster absorbing subpopulation of subjects, assuming each subject should have an expected Cmax for LTX-04P consistent with the average seen in the 1 and 2 tablets subgroups of 53% of Dilaudid, the subpopulations demonstrated:

  • 82% of subjects had an estimated reduction in Cmax associated with LIMITX
  • 38% average estimated reduction in Cmax associated with LIMITX
  • 66% maximum reduction in estimated Cmax observed in two of 17 subjects
  • 1.6x average increase in Tmax associated with LIMITX

We have commenced reformulation work on the LIMITX Technology micro-particles to improve the drug delivery with one and two tablets. We intend to discuss with the FDA the Study 400 results and the next clinical phase under its Fast Track development designation for LTX-04.


Formulation development work was initiated for LTX-03 in March 2016.