APTX is an abbreviation of "Apoptoxin," and, as the name implies, it involves the activation of uncontrolled apoptosis which causes death by the destruction of cells. In addition, it can also activate telomerase. The original purpose of the compound, as hinted by Haibara herself, is "to raise the dead", indicating an intent to control biological life.
However, in very rare cases, it causes the apoptosis of non-neural cells only and the apoptosis would stabilize at some point, causing the victim's apparent age to be decreased. Shinichi, the series' protagonist, is such a victim; later Shiho Miyano, who chooses to attempt suicide by using her own drug, was added to the two known people to have survive after taking the APTX-4869 throughout the series.
Reversing the effects Edit
Throughout the series there are several instances in which the APTX was temporarily neutralized and Shinichi and Shiho were returned to their actual age forms. The main ingredient for this reversal is a component found in Chinese ginseng root schnaps, which Ai has already incorporated in a prototype antidote for the APTX.
It is to note that in the instances where Shinichi or Shiho were successfully changed back, the recipient was suffering from a common cold while the component was ingested, indicating that the immune system somehow has to be taxed for the antidote to work. While not canon, Crossroad in the Ancient Capital uses this idea as Conan is given a pill to give him the symptoms of a cold, while drinking Baigar.
At first, it was revealed by Gin that the APTX 4869 was a poison to kill people who know too much about the Black Organization. He used Shinichi as a guinea pig. Shiho Miyano said that she didn't intend to create a poison, which suggests that APTX 4869 was originally developed with a different goal in mind. It probably was just a useful side effect that the current prototype kills while leaving no trace in the victim’s body, and was thus employed as a poison - a usage which Haibara detests. Additionally, APTX 4869 is nicknamed the "incomplete detective" by the Black Organization, which means its true purpose has not yet been achieved.
One possibility is that the goal of the APTX 4869 is to develop a therapy which will cause immortality, stall or reverse the effects of aging, or extend a human's lifespan. The de-aging effect that occurred when Shinichi and Haibara took APTX 4869 probably indicates the main intent of the drug's development. After Pisco saw Haibara shrink back to her child form, he commented that he was impressed she had developed the drug to that point, implying that deaging is in the right direction.Supporting this is Haibara’s line, "Kudo-kun? You would probably never even dream that you are already part of a project the Black Organization has been working on already for half a century." APTX 4869 is the only known intersection between Shinichi and the Black Organization; meaning that Shinichi's de-aging made him relevant to the Black Organization's project.
According to Haibara’s description about APTX 4869, APTX 4869 activates telomerase, an enzyme which can increase the number of times a cell can divide, and therefore affect a cell's lifespan and “reproductive potential”. The goal of this might be to revert all non-neural cells to a "youthful", high reproductive potential state. Vermouth's unnatural youth is another indicator that the Black Organization may be involved in research towards extending lifespan, halting aging, or rejuvenating the body.
The goal of the antagonists in Magic Kaito is pursuing immortality, via the Pandora Gem, but it is unclear whether if the organization in Magic Kaito is the same one as the Black Organization.
Raising the deadEdit
The original purpose of APTX 4869 might be to raise the dead. Once when Conan asked Haibara directly what APTX 4869 was meant to do she replied, "It's a nostrum to raise the dead. I wonder if that answer is satisfactory?" The context of the comment, however, makes it unclear if she was merely bluffing to provoke Conan into revealing that he had been looking into the Black Organization behind her back, rather than making a serious statement of the purpose of the drug.
"Silver Bullet" and "APTX 4869" are two names for the same projectEdit
In a flashback, Shiho recalls the end of the recorded message left by her mother which revealed Elena had been working on "a truly terrifying drug" the Miyano parents called the Silver Bullet. It is unclear whether Silver Bullet is the Miyano parents' personal nickname for what is currently called APTX 4869, or if it was a closely related project they developed in parallel. Whatever the case, Silver Bullet and APTX 4869 are probably closely linked if not the same in-development drug. Haibara took over her parents' research after they died, with the APTX project named specifically. After watching Haibara shrink, Pisco, who knew about the project the Miyanos worked on, commented that Shiho's parents would be proud of the progress Shiho had made on the drug. In addition, Haibara had earlier referred to APTX 4869 as a dream-like drug. the same expression Elena's labmates used to describe Silver Bullet. During her recollection of the tapes, Haibara was holding and considering the antidote to APTX 4869. She then regrets that she didn't understand the drug was something that should have never been made, strongly implying she worked on the same drug as well. Lastly, Vermouth, who was in the Organization long enough to have heard the Miyanos use the name "Silver Bullet",may have given Conan the same nickname in reference to his deaged state caused by the drug.
APTX 4869 is a pun on "Sherlock Holmes". 4869 can also be pronounced "Shi-Ya-Ro-Ku", which translates into Sherlock. Adding to the pun, the password for the APTX data is "Shellingford", an unintentional misspelling of "Sherrinford", which was the name Arthur Conan Doyle called his detective character before deciding on "Sherlock". The password and the pun name seem to be related to why several members of the Black Organization call APTX 4869 the "incomplete detective",implying APTX 4869 is not finished yet.